Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

Method and apparatus for optically stimulating neurons of a plurality of
auditory nerve pathways of a person to provide auditory sensations for
the person by generating a plurality of pulsed light signals having one
or more successive pulses. The spectrum of a detected audio signal is
divided into M channels. In some embodiments, an N-of-M coding strategy
is employed, where, for any given time frame, only N of the M channels
are selected and illuminated to stimulate the auditory nerves. In some
embodiments, the M channels are organized into bins, where, for any given
time frame, only a maximum number of channels are illuminated per bin.
This limits the number of illuminated channels-per-length of cochlea and
therefore prevents localized heating of the cochlea and reduces power
consumption of the device.

Claims:

1. A method comprising: obtaining an audio signal having an audio
spectrum; for each of a plurality of successive time frames including a
first, second, third and fourth time frame, generating a plurality of "M"
audio channels of the audio spectrum, each of the plurality of "M" audio
channels for one of the plurality of time frames having a sub-portion of
frequencies of the audio spectrum for a period of time corresponding to
that one of the plurality of frames; and for each of the plurality of
time frames: selecting a subset of "N" audio channels selected from the
"M" audio channels by an "N of M" coding strategy; for each one of the
subset of "N" audio channels, generating a corresponding pulsed light
signal having one or more successive pulses that, when applied to a
neuron of a person, will each stimulate a nerve action potential (NAP) in
the neuron; and delivering the generated corresponding pulsed light
signals to a corresponding one of a plurality of frequency-specific
locations in the cochlea of the person to optically stimulate one or more
neurons in the cochlea in order to trigger NAPs in the one or more
neurons of the cochlea.

2. The method of claim 1, wherein the plurality of "M" audio channels are
organized into a plurality of bins, each of the plurality of bins having
a plurality of audio channels, and wherein, for each bin, the selected
subset of "N" audio channels includes a maximum of fewer than all audio
channels within that one bin.

3. The method of claim 2, wherein adjacent ones of the audio channels of
the plurality of audio channels in each bin are directed towards neurons
that, when triggered, are perceived by the person to be adjacent to each
other in frequency.

4. The method of claim 3, wherein selecting the subset of "N" audio
channels includes selecting an individual one of the "M" audio channels
at no more than two successive time frames during the plurality of
successive time frames.

5. The method of claim 1, wherein the selected subset of "N" audio
channels during the first time frame includes eleven audio channels
corresponding to eleven portions of the audio spectrum having a strongest
signal selected from the "M" audio channels during the first time frame,
and wherein the first time frame is in a range between approximately 4
milliseconds and approximately 7.5 milliseconds.

6. The method of claim 1, wherein the selecting of the subset of "N"
audio channels includes limiting selection of an individual one of the
"M" audio channels to be in no more than two successive time frames
during the plurality of successive time frames.

7. An apparatus for optically stimulating neurons of a cochlea of a
person, the apparatus comprising: means for obtaining an audio signal
having an audio spectrum; means for generating a plurality of "M" audio
channels of the audio spectrum for each of a plurality of successive time
frames including a first, second, third and fourth time frame, each of
the plurality of "M" audio channels for one of the plurality of time
frames having a sub-portion of frequencies of the audio spectrum for a
period of time corresponding to that one of the plurality of frames;
means for selecting for each of the plurality of time frames a subset of
"N" audio channels selected from the "M" audio channels by an "N of M"
coding strategy; means for generating for each of the plurality of time
frames a corresponding pulsed light signal having one or more successive
pulses for each one of the subset of "N" audio channels that, when
applied to a neuron of a person, will each stimulate a nerve action
potential (NAP) in the neuron; and means for delivering for each of the
plurality of time frames the generated corresponding pulsed light signals
to a corresponding one of a plurality of frequency-specific locations in
the cochlea of the person to optically stimulate one or more neurons in
the cochlea in order to trigger NAPs in the one or more neurons of the
cochlea.

8. The apparatus of claim 7, wherein the plurality of "M" audio channels
are organized into a plurality of bins, each of the plurality of bins
having a plurality of audio channels, and wherein, for each bin, the
selected subset of "N" audio channels includes a maximum of fewer than
all audio channels within that one bin.

9. The apparatus of claim 7, wherein the plurality of "M" audio channels
are organized into a plurality of bins, each of the plurality of bins
having a plurality of the plurality of audio channels, and wherein, for
each bin, the selected subset of "N" audio channels includes a maximum of
fewer than all audio channels within that one bin, and wherein the means
for selecting the subset of "N" audio channels includes means for
selecting a minimum of at least "X" audio channels from each of the
plurality of bins, and means for selecting a maximum of no more than "Y"
audio channels from each of the plurality of bins.

10. The apparatus of claim 7, wherein a subset of the plurality of audio
channels in each bin is also in an adjacent bin, wherein a first
frequency range covered by the adjacent audio channels in a first bin
partially overlaps with a second frequency range covered by the adjacent
audio channels in a second bin.

11. The apparatus of claim 7, wherein the means for selecting the subset
of "N" audio channels includes selecting an individual one of the "M"
audio channels at no more than two successive time frames during the
plurality of successive time frames.

12. The apparatus of claim 7, wherein the means for selecting is further
configured to select the subset of "N" audio channels, such that an
individual one of the "M" audio channels is selected at no more than two
successive time frames during the plurality of successive time frames.

13. The apparatus of claim 7, wherein the means for selecting is further
configured to select the subset of "N" audio channels during the first
time frame such that eleven audio channels corresponding to eleven
portions of the audio spectrum having a strongest signal are selected
from the "M" audio channels during the first time frame, and wherein the
first time frame is in a range of approximately 4 milliseconds to 7.5
milliseconds.

14. An apparatus for optically stimulating neurons of a cochlea of a
person, the apparatus comprising: an audio sensor configured to obtain an
audio signal having an audio spectrum; an audio processor configured to
generate a plurality of "M" audio channels of the audio spectrum for each
of a plurality of successive time frames including a first, second, third
and fourth time frame, each of the plurality of "M" audio channels for
one of the plurality of time frames having a sub-portion of frequencies
of the audio spectrum for a period of time corresponding to that one of
the plurality of frames; a channel mapper configured to select for each
of the plurality of time frames a subset of "N" audio channels selected
from the "M" audio channels by an "N of M" coding strategy; an optical
generator configured to output, for each of the plurality of time frames,
a corresponding pulsed light signal having one or more successive pulses
for each one of the subset of "N" audio channels that, when applied to a
neuron of a person, will each stimulate a nerve action potential (NAP) in
the neuron; and an optical guide configured to deliver, for each of the
plurality of time frames, the generated corresponding pulsed light
signals to a corresponding one of a plurality of frequency-specific
locations in the cochlea of the person to optically stimulate one or more
neurons in the cochlea in order to trigger NAPS in the one or more
neurons of the cochlea.

15. The apparatus of claim 14, wherein the plurality of "M" audio
channels are organized into a plurality of bins, each of the plurality of
bins having a plurality of audio channels, and wherein, for each bin, the
selected subset of "N" audio channels includes a maximum of fewer than
all audio channels within that one bin.

16. The apparatus of claim 14, wherein the plurality of "M" audio
channels are organized into a plurality of bins, each of the plurality of
bins having a plurality of audio channels, and wherein, for each bin, the
selected subset of "N" audio channels includes a maximum of fewer than
all audio channels within that one bin, and wherein the channel mapper is
further configured to select the subset of "N" audio channels, wherein
the subset of "N" audio channels are chosen such that a minimum of at
least "X" audio channels is selected from each of the plurality of bins,
and a maximum of no more than "Y" audio channels are selected from each
of the plurality of bins.

17. The apparatus of claim 14, wherein adjacent ones of the audio
channels of the plurality of audio channels in each bin are directed
towards neurons that, when triggered, are perceived by the person to be
adjacent to each other in frequency.

18. The apparatus of claim 17, wherein a subset of the plurality of audio
channels in each bin is also in an adjacent bin, wherein a first
frequency range covered by the adjacent audio channels in a first bin
partially overlaps with a second frequency range covered by the adjacent
audio channels in a second bin.

19. The apparatus of claim 14, wherein the channel mapper is further
configured to select the subset of "N" audio channels, wherein the subset
of "N" audio channels is selected such that an individual one of the "M"
audio channels is selected at no more than two successive time frames
during the plurality of successive time frames.

20. The apparatus of claim 14, wherein the selected subset of "N" audio
channels during the first time frame includes eleven audio channels
corresponding to eleven portions of the audio spectrum having a strongest
signal selected from the "M" audio channels during the first time frame,
and wherein the first time frame is in a range of approximately 4
milliseconds to 7.5 milliseconds.

[0009] U.S. patent application No. 13/______ filed on even date herewith
by Ryan C. Stafford et al. and titled "OPTIMIZED STIMULATION RATE OF AN
OPTICALLY STIMULATING COCHLEAR IMPLANT" (Attorney Docket 5032.080US1),
each of which is incorporated herein by reference in its entirety.

[0029] The invention relates generally to optical stimulation of nerves to
restore hearing, and more particularly to apparatus and methods for using
an N of M coding strategy to minimize local heating of the cochlea and
thereby preventing damage to the cochlea.

BACKGROUND OF THE INVENTION

[0030] The commercialization of cochlear implants, which directly
stimulate the auditory nerve to provide hearing to the profoundly deaf,
is somewhat recent (introduced in 1984 as an FDA-approved device). These
conventional devices utilize the compound nerve action potential (CNAP)
produced by the presence of an electric field in proximity of the spiral
ganglion cells within the cochlea. In such conventional devices, acoustic
sounds from the environment are digitized, separated into a plurality of
frequency bands (called "audio-frequency channels" herein) and the
loudness envelope of the signal in all of the audio-frequency channels
carries the information necessary to generate electrical signals to
stimulate cochlear nerves to allow the patient to perceive speech and
other pertinent sounds. In electrical cochlear implants, pulsatile
electric currents are modulated in amplitude to convey this information
to the listener. Pulse-repetition rate and pulse width would typically be
held constant, while pulse amplitude is modulated to follow relative
changes in loudness. While electrical cochlear implants can be effective,
they often lack the specificity to target the desired auditory nerve
pathway without also activating other auditory nerve pathways as a side
effect (because electrical current spreads in the body, most if not all
neuromodulation devices wind up stimulating other nerves in the area
besides the intended target (thus potentially causing, for example,
unintended hearing sensations)). The presence of a stimulation artifact
can also obfuscate signals elsewhere along the auditory nerve, which
precludes stimulating and recording electrical nerve activity in the same
location.

[0031] As used herein, the auditory-nerve pathway includes all of the
nerves from and including the cochlea, to and including the brain stem.

[0032] The discovery that neural compound action potentials (CAPs) can be
evoked by pulsed optical stimulation has led to development of cochlear
implants based on optical stimulation (e.g., see U.S. Pat. No. 8,012,189
issued Sep. 6, 2011 to James S. Webb et al., titled "Vestibular Implant
using Optical Stimulation Of Nerves" (Attorney Docket 5032.026US1), and
U.S. Patent Application Publication US 2011/0295331 of Jonathon D. Wells
et al., dated Dec. 1, 2011 and titled "Laser-Based Nerve Stimulators for,
e.g., Hearing Restoration in Cochlear Prostheses" (Attorney Docket
5032.063US1), both of which are incorporated herein by reference, and
both of which are assigned to Lockheed Martin Corporation, the assignee
of the present invention). Optical stimulation provides more precise
neural stimulation compared to electrical stimulation methods because
light is directed in a single direction, and there is no stimulation
artifact. However, the physiological mechanism of optical stimulation is
different than that of electrical stimulation. This leads to the
challenge of encoding the information for the listener in a way that
optimally exploits the physiological mechanism of optical stimulation.

[0033] U.S. Patent Application Publication US 2010/0049180 of Jonathon D.
Wells et al., dated Feb. 25, 2010 and titled "System and Method for
Conditioning Animal Tissue using Laser Light" (Attorney Docket
5032.039US1), is incorporated herein by reference in its entirety. Wells
et al. describe systems and methods for prophylactic measures aimed at
improving wound repair. In some embodiments, laser-mediated
preconditioning would enhance surgical wound healing that was correlated
with hsp70 expression. Using a pulsed laser (λ=1850 nm, Tp=2 ms, 50
Hz (in this context, Hz means stimulation pulses per second (pps)),
H=7.64 mJ/cm2) the skin of transgenic mice that contain an hsp70
promoter-driven luciferase were preconditioned 12 hours before surgical
incisions were made. Laser protocols were optimized using temperature,
blood flow, and hsp70-mediated bioluminescence measurements as
benchmarks. Bioluminescent imaging studies in vivo indicated that an
optimized laser protocol increased hsp70 expression by 15-fold. Under
these conditions, healed areas from incisions that were
laser-preconditioned were two times stronger than those from control
wounds. Though useful for wound treatment and surgical pre-treating,
chronic heating of tissue (such as the cochlea) is detrimental.

[0047] There is a need for an improved apparatus and a corresponding
method for optical (and optionally optical combined with electrical)
stimulation of nerves to restore hearing.

BRIEF SUMMARY OF THE INVENTION

[0048] In some embodiments, the present invention provides an apparatus
that includes an infrared (IR) light source wherein the IR light provides
optical stimulation of auditory nerves to generate nerve-action
potentials (NAPs) in one or more individual nerve cells, and/or compound
nerve-action potentials (CNAPs) in a nerve bundle. In some embodiments,
the stimulation of NAPs and CNAPs is used to restore hearing.

[0049] In electrical stimulation, the challenging problem is the spreading
of the electrical signal through the conductive fluid and tissue in the
cochlea. Optical stimulation does not suffer this problem and therefore
has an advantage in its ability to stimulate in a more specific manner,
which leads to higher spectral fidelity for the implantee. One challenge,
however, is heating of the tissue by the optical channels. Because the
physiological mechanism for stimulation using optical signals is thermal,
careful engineering is needed to allay thermal buildup in the cochlea.

[0050] In some embodiments, an N of M coding strategy is used, while
placing a quota (i.e., a limit) on the number of optical-stimulation
channels selected to illuminate in each frame. Speech tends to fill the
audio frequency spectrum between 50-6000 Hz and conventional
electrical-stimulation cochlear implant speech processors tend to cover
the range 240-6000 Hz, depending on insertion depth. In some embodiments
of the present optical-simulation cochlear-implant invention, an audio
range of 50-6000 Hz or other suitable range is used, wherein this total
audio range is broken into 22 (or other suitable number of)
audio-frequency channels and 11 (or other suitable subset number of)
these audio-frequency channels are illuminated at each time-frame cycle
(sometimes simply called "frame" herein). In other embodiments, rather
than simply illuminate the 11 frequency-based channels of the detected
audio spectrum having the highest power during a given time-frame cycle,
there is a quota to illuminate at least X optical-stimulation channels
from each bin of optical-stimulation channels (wherein, in some
embodiments, for some bins, X is zero or more, while for other bins, X
may be one, two, or more channels) and no more than Y optical-stimulation
channels from each bin. This limits the number of illuminated
optical-stimulation channels-per-length of cochlea and therefore prevents
localized heating of the cochlea and reduces power consumption of the
device. In some embodiments, rather than using non-overlapping bins
(wherein the lowest-frequency channels of one bin could be contiguous
with the highest-frequency channels of an adjacent bin), overlapping bins
are used, such that the Y limit on optical-stimulation channels (i.e.,
how many optical-stimulation channels in one bin that are allowed to be
active in a given predetermined period of time) applies to adjacent areas
that might have been in different bins if non-overlapping bins were to be
used.

[0051] This solution provides the advantages of optical stimulation while
minimizing the risk of damage to cochlear nerves or other cochlear tissue
from overheating.

BRIEF DESCRIPTION OF THE FIGURES

[0052] Each of the items shown in the figures described in the following
brief description of the drawings represents some embodiments of the
present invention.

[0053] FIG. 1 is a schematic representation of a system 100 with a
hardware- and operating-environment having an implanted device 110, an
optional externally worn device 111 and a customization console computer
20.

[0057] FIG. 3A is a schematic diagram of a broadband wavelength source 310
having a designed power/wavelength spectrum profile formed to customize
the absorption of optical power in the tissue of interest.

[0058] FIG. 3B includes a schematic graph 307A of a tissue sensitivity to
optical stimulation for a first given type or composition of tissue as a
function of the wavelength of the optical stimulation.

[0059]FIG. 3C is a schematic diagram of a broadband wavelength source 320
having a designed power/wavelength spectrum profile formed to customize
the absorption of optical power in the tissue of interest.

[0060] FIG. 3D is a schematic graph 308A of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue.

[0061] FIG. 3E is a schematic diagram of a broadband wavelength source 330
having a designed power/wavelength spectrum profile formed to customize
the absorption of optical power in the tissue of interest.

[0062] FIG. 3F is a schematic graph 309A of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue.

[0063] FIG. 3G is a schematic graph 307B of a tissue sensitivity to
optical stimulation for a second given type or composition of tissue as a
function of the wavelength of the optical stimulation.

[0064] FIG. 3H is a schematic graph 308B of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue.

[0065] FIG. 3I is a schematic graph 309B of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue.

[0066] FIG. 3J includes schematic graphs 307C, 307D, and 307E of tissue
sensitivity to optical stimulation for a three types or compositions of
tissue as a function of the wavelength of the optical stimulation.

[0067] FIG. 3K is a schematic graph 308C of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
plurality of tissues.

[0068] FIG. 3L is a schematic graph 309C of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
plurality of tissues.

[0069] FIG. 3M includes a computer-simulation-derived plot of a
temperature profile of tissue due to absorption of single-wavelength
source 331 (see, e.g., FIG. 4A) of infrared light having a first
wavelength.

[0070] FIG. 4 is a plot of a temperature profile of tissue due to
absorption of single-wavelength source of infrared light.

[0071] FIG. 4A is a schematic diagram that includes a plot of a
temperature profile of tissue due to absorption of single-wavelength
source 331 of infrared light having a first wavelength.

[0072] FIG. 4B is a schematic diagram that includes a plot of a
temperature profile of tissue due to absorption of single-wavelength
source 332 of infrared light having a second wavelength.

[0073] FIG. 4C is a schematic diagram that includes a plot of a
temperature profile of tissue due to absorption of single-wavelength
source 333 of infrared light having a third wavelength.

[0074] FIG. 4D is a schematic diagram that includes a plot of a
temperature profile of tissue due to absorption of source 330A of
infrared light having a customized spectrum of wavelengths.

[0075]FIG. 4E is a schematic diagram that includes a plot of a
temperature profile of tissue due to absorption of source 330B of
infrared light having a customized spectrum of wavelengths.

[0076] FIG. 4F is a schematic graph 409A of a designed power/wavelength
spectrum profile for a time period N in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues.

[0077] FIG. 4G is a schematic graph 409B of a designed power/wavelength
spectrum profile for a time period N+1 in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues.

[0078] FIG. 4H is a schematic graph 409C of a designed power/wavelength
spectrum profile for a time period N+2 in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues.

[0079] FIG. 5 is a schematic representation of a system 500 having an
implanted device 110, an optional externally worn device 111 and a
transceiver 71 of customization console computer such as shown in FIG. 1.

[0080] FIG. 6A is a flow chart of a method 601, according to some
embodiments of the present invention.

[0081] FIG. 6B is a flow chart of a method 602, according to some
embodiments of the present invention.

[0082] FIG. 7 is a flow chart of a method 700, according to some
embodiments of the present invention.

[0083] FIG. 8A is a flow chart of a method 801, according to some
embodiments of the present invention.

[0084] FIG. 8B is a graph of a binned-channel-with-history spectrum 802,
according to some embodiments of the present invention.

[0085] FIG. 9 is a flow chart of a method 900, according to some
embodiments of the present invention.

[0086] FIG. 10 is a flow chart of a method 1000, according to some
embodiments of the present invention.

[0087]FIG. 11 is a diagram of the firing of auditory nerve cells 1100 as
hair cells are deflected.

[0099] FIG. 19 is a graph 1900 of phoneme recognition as a function of
stimulation rate.

[0100] FIG. 20 is a graph 2000 of phoneme recognition as a function of
stimulus dynamic range.

DETAILED DESCRIPTION OF THE INVENTION

[0101] Although the following detailed description contains many specifics
for the purpose of illustration, a person of ordinary skill in the art
will appreciate that many variations and alterations to the following
details are within the scope of the invention. Very narrow and specific
examples are used to illustrate particular embodiments; however, the
invention described in the claims is not intended to be limited to only
these examples, but rather includes the full scope of the attached
claims. Accordingly, the following preferred embodiments of the invention
are set forth without any loss of generality to, and without imposing
limitations upon the claimed invention. Further, in the following
detailed description of the preferred embodiments, reference is made to
the accompanying drawings that form a part hereof, and in which are shown
by way of illustration specific embodiments in which the invention may be
practiced. It is understood that other embodiments may be utilized and
structural changes may be made without departing from the scope of the
present invention.

[0102] The embodiments shown in the Figures and described here may include
features that are not included in all specific embodiments. A particular
embodiment may include only a subset of all of the features described, or
a particular embodiment may include all of the features described.

[0103] The leading digit(s) of reference numbers appearing in the Figures
generally corresponds to the Figure number in which that component is
first introduced, such that the same reference number is used throughout
to refer to an identical component which appears in multiple Figures.
Signals and connections may be referred to by the same reference number
or label, and the actual meaning will be clear from its use in the
context of the description.

[0104] FIG. 1 is an overview diagram of a hardware- and
operating-environment (or system) 100 that is used in conjunction with
embodiments of the invention. The description of FIG. 1 is intended to
provide a brief, general description of suitable computer hardware and a
suitable computing environment in conjunction with which the invention
may be implemented. In some embodiments, the invention is described in
the general context of computer-executable instructions, such as program
modules, that are stored on computer-readable media and that are executed
by a computer, such as a microprocessor residing in an implanted device
(located within a patient) and/or in an external device worn by the
patient and/or personal computer that is/are wirelessly linked to the
implanted device. Generally, program modules include routines, programs,
objects, components, data structures, and the like, that perform
particular tasks or implement particular abstract data types.

[0105] In some embodiments, system 100 includes an audiologist- and/or
user-control console computer 20 that is programmable and that has a
wireless transceiver 71 that allows wireless control (i.e., reprogramming
of the remote microprocessors) of the implanted device 110 (which
includes a programmed microcontroller), and/or an externally worn device
111 (which also includes a programmed microcontroller) that wirelessly
communicates and/or provides power to the implanted device 110. In some
embodiments, application programs 36 stored on a computer-readable
storage device (e.g., optical disk 31 (CDROM, DVD, Blu-ray Disc® (BD),
or the like), magnetic or FLASH storage device 29 (e.g., floppy disk,
thumb drive, SDHC® (Secure-Data High-Capacity) memory card or the
like), and/or a storage device 50 connected to a remote computer 49 that
connects to computer 20 across a local-area network 51 or a wide-area
network 52 such as the internet) contain instructions and/or control
structures (such as look-up tables, control parameters, databases and the
like) that are processed and/or transmitted into the implanted device 110
to control its operation by methods of the present invention described
herein. In some embodiments, the applications programs 36 are partially
executed in the computer 20 and/or the externally worn device 111, and
then partially executed in the implanted device 110.

[0106] Accordingly, in some embodiments, an audiologist and/or user can
adjust parameters of the implanted
optical-electrical-cochlear-stimulation device 110 to customize its
operation to a much greater extent than is possible with a conventional
electrical-stimulation cochlear implant, because implanted
optical-electrical-cochlear-stimulation device 110 has a far greater
number of parameters that can be finely adjusted (e.g., pulse width,
amplitude, frequency, wavelength, polarization, wavelength profile, beam
profile, beam angle, and, the like). In some embodiments, the
applications programs 36 contain a'substantial amount of safety control
code that runs in computer 20 to guide the audiologist and/or user to
adjust the parameters of the implanted optical-cochlear-stimulation
device 110 and to help prevent operation that might harm the patient or
damage the implanted device 110 (such as what might occur if too much
optical energy were applied in a concentrated small area of the cochlea
or within too short a period of time, or if overheating occurred in the
device 110 due to too many VCSELs (vertical-cavity surface emitting
lasers) next to one another being activated in a short period of time).

[0107] Although many of the embodiments herein have light-emitting
elements that include VCSELs (vertical-cavity surface emitting lasers)
implemented as electrically pumped semiconductor diode lasers, other
embodiments of the present invention use edge-emitting semiconductor
diode lasers, optically pumped semiconductor lasers, optically pumped
optical-fiber lasers, light-emitting diodes, superluminescent devices, or
any other suitable light source. Some embodiments use wavelengths in the
range of 1.75 microns to 2 microns, other embodiments use any other
suitable wavelengths.

[0108] Moreover, those skilled in the art will appreciate that the
invention may be practiced with other computer-system configurations,
including hand-held devices, multiprocessor systems, microprocessor-based
or programmable consumer electronics, network PCs, minicomputers,
mainframe computers, and the like. The invention may also be practiced in
distributed computer environments where tasks are performed by remote
processing and input-output (I/O) devices that are linked through a
communications network. In a distributed-computing environment, program
modules may be located in both local and remote storage devices.

[0109] As shown in FIG. 1, in some embodiments, the hardware- and
operating-environment includes audiologist- and/or user-control console
computer 20, or a server 20, including a processing unit 21, a system
memory 22, and a system bus 23 that operatively couples various system
components including the system memory 22 to the processing unit 21. In
some embodiments, there may be only one, or in other embodiments, there
may be more than one processing unit 21, such that the processor of
computer 20 comprises a single central-processing unit (CPU), or a
plurality of processing units, commonly referred to as a multi-processor
or parallel-processing environment. In various embodiments, computer 20
may be implemented using a conventional computer, a distributed computer,
or any other type of computer including those embedded in cell phones,
personal-data-assistant devices or other form factors.

[0110] The system bus 23 can be any of several types of bus structures
including a memory bus or memory controller, a peripheral bus, and a
local bus using any of a variety of bus architectures. The system memory
can also be referred to as simply the memory, and includes read-only
memory (ROM) 24 and random-access memory (RAM) 25. A basic input/output
system (BIOS) 26, containing the basic routines that help to transfer
information between elements within the computer (or server) 20, such as
during start-up, may be stored in ROM 24. The computer 20 further
includes a hard disk drive 27 for reading from and writing to a magnetic
hard disk, a removable-media drive or FLASH controller 28 for reading
from or writing to a removable magnetic floppy-disk or FLASH storage
device 29, and an optical disk drive 30 for reading from or writing to a
removable optical disk 31 (such as a CDROM, DVD, Blu-ray Disc® (BD) or
other optical media).

[0111] The hard disk drive 27, magnetic disk drive 28, and optical disk
drive 30 couple with a hard disk drive interface 32, a magnetic disk
drive interface 33, and an optical disk drive interface 34, respectively.
The drives and their associated computer-readable media provide
non-volatile, non-ephemeral storage of computer-readable instructions,
data structures, program modules and other data for the computer 20. It
should be appreciated by those skilled in the art that any type of
computer-readable media which can store data that is accessible by a
computer, such as magnetic cassettes, FLASH memory cards, digital video
disks, Bernoulli cartridges, random-access memories (RAMs), read-only
memories (ROMs), redundant arrays of independent disks (e.g., RAID
storage devices) and the like, can be used in the exemplary operating
environment.

[0112] A plurality of program modules that implement the optimization
methods of the present invention can be stored on the hard disk, magnetic
or FLASH storage device 29, optical disk 31, ROM 24, or RAM 25, including
an operating system 35, one or more application programs 36, other
program modules 37, and program data 38. A plug-in program containing a
security transmission engine for the present invention can be resident on
any one, or on a plurality of these computer-readable media.

[0113] In some embodiments, a user (e.g., the audiologist or the patient)
enters commands and perception information into the computer 20 through
input devices such as a keyboard 40, pointing device 42 or other suitable
device such as a microphone (not shown). Other input and/or output
devices (not shown) can include a microphone, joystick, game pad,
satellite dish, scanner, speaker, headphones or the like. These other
input and output devices are often connected to the processing unit 21
through a serial port interface 46 that is coupled to the system bus 23,
but can be connected by other interfaces, such as a parallel port, game
port, or a universal serial bus (USB); a monitor 47 or other type of
display device can also be connected to the system bus 23 via an
interface, such as a video adapter 48. The monitor 47 can display a
graphical user interface for the audiologist and/or user. In addition to
the monitor 47, computers typically include other peripheral output
devices (not shown), such as speakers and printers.

[0114] In some embodiments, computer 20 operates in a networked
environment using logical connections to one or more remote computers or
servers, such as remote computer 49. These logical connections are
achieved by a communication device coupled to or a part of the computer
20; the invention is not limited to a particular type of communications
device. The remote computer 49 can be another computer, a server, a
router, a network PC, a client, a peer device or other common network
node, and typically includes many or all of the elements described above
relative to the computer 20, although only memory storage device 50 and
application programs 36 have been illustrated in FIG. 1. The logical
connections depicted in FIG. 1 include local-area network (LAN) 51 and
wide-area network (WAN) 52. Such networking environments are commonplace
in office networks, enterprise-wide computer networks, intranets and the
Internet, which are all types of networks.

[0115] When used in a local-area networking (LAN) environment, the
computer 20 is connected to the LAN 51 through a network interface, modem
or adapter 53, which is one type of communications device. When used in a
wide-area networking (WAN) environment such as the internet, the computer
20 typically includes an adaptor or modem 54 (a type of communications
device), or any other type of communications device, e.g., a wireless
transceiver, for establishing communications over the wide area network
52, such as the internet. The modem 54, which may be internal or
external, is connected to the system bus 23 via the serial port interface
46. In a networked environment, program modules depicted relative to the
personal computer 20, or portions thereof, (or those stored in the
externally worn device 111 or the implanted device 110) can be stored in
the remote memory storage device 50 of remote computer (or server) 49 and
accessed over the interne or other communications means. Note that the
transitory signals on the internet may move stored program code from a
non-transitory storage medium at one location to a computer that executes
the code at another location by the signals on one or more networks. The
program instructions and data structures obtained from a network or the
internet are not "stored" on the network itself, but are stored in
non-transitory storage media that may be connected to the internet from
time to time for access. It is appreciated that the network connections
shown are exemplary, and in some embodiments, other means of, and
communications devices for, establishing a communications link between
the computers may be used including hybrid fiber-coax connections, T1-T3
lines, DSL's, OC-3 and/or OC-12, TCP/IP, microwave, WAP (wireless
application protocol), and all other electronic media through standard
switches, routers, outlets and power lines, as the same are known and
understood by one of ordinary skill in the art.

[0116] The hardware and operating environment in conjunction with which
embodiments of the invention may be practiced has been described. The
computer 20 in conjunction with which embodiments of the invention can be
practiced can be a conventional computer, a distributed computer, or any
other type of computer; the invention is not so limited. Such a computer
20 typically includes one or more processing units as its processor, and
a computer-readable medium such as a memory. The computer 20 can also
include a communications device such as a network adapter or a modem, so
that it is able to communicatively couple to other computers, servers, or
devices.

[0117] In some embodiments, one or more parts of system 100 elicits and
receives input from a user, and based on the input, modifies, adjusts or
executes one or more of the methods of the present invention as described
herein.

[0118] FIG. 2A is a schematic diagram of a VCSEL-based implanted
stimulation system 200 that is coiled from a base end (that is
electrically connected to a driver circuit 250 via electrical connection
substrate ribbon 212) to an apex end, such that the coiling of system 200
matches the coiling of cochlea 85 and is inserted into cochlea 85. In
some embodiments, system 200 is configured to be inserted within a length
of cochlea 85 (forming the inserted intra-cochlear portion 210), while in
other embodiments, system 200 is configured to be placed outside and
along the exterior of cochlea 85. In some embodiments, system 200
includes a plurality of VCSEL sources 244 configured to direct optically
stimulating light pulses to excitable tissue in the cochlea of a person
in order to trigger nerve action potentials in one or more auditory nerve
pathways of the cochlea.

[0119] The basilar membrane within the cochlea 85 of the inner ear is a
stiff structural element that separates two liquid-filled tubes (the
scala media 86 and the scala tympani 89) that run along the coil of the
cochlea, and that contains the organ of corti 88. A third liquid-filled
tube that runs along the coil of the cochlea, the scala vestibuli 87, is
separated from the scala media 86 by Reissner's membrane, and has a fluid
that is different than that of the scala media 88 and the scala tympani
89. High frequencies are detected by nerves nearest the basal end (where
the basilar membrane is stiffest), while low frequencies are detected by
nerves nearest the apical end of the cochlea 85. Thus, when an
optical-stimulation device cannot be inserted far enough towards the
apical end, it is the low-frequency sensations that cannot be stimulated.
Therefore, in some embodiments, the intra-cochlear portion 210 of system
200 includes one or more signal electrodes 246 (in some embodiments, the
intra-cochlear portion 210 optionally includes one or more return (or
ground) electrodes 247 to provide a nearby electrical ground for return
current in a portion of the cochlea across from the electrodes 246, so as
to provide an electrical field that extends across one or more
stimulate-able nerves in the cochlea. In other embodiments, electrodes
are arranged in pairs of (or groups of two or more) electrodes that are
driven by bi-phasic differential electrical-stimulation signals, either
of which, at different times can be more positive than the other, and the
signals are generated to prevent ionic-charge build-up in the tissue
located deep in the apical end of cochlea 85.

[0120] In some such embodiments, electrodes 246 are configured to provide
electrical stimulation for the apical spiral ganglion cells at the lower
frequency range. Electrical stimulation can access these deeper regions
of cochlea 85 because of the spread of electricity that occurs during
electrical stimulation (in some embodiments, there is no spreading of the
optical signal to illuminate the cells beyond the tip of the last VCSEL
source 244). In some embodiments, the one or more electrodes 246 are
covered by an insulating sheath 245 that is configured to electrically
isolate the one or more intra-cochlear electrodes 246 (and optionally
247) from each other and to help orient the electrical field between the
intra-cochlear electrode(s). In some embodiments, insulating sheath 245
is further configured to electrically isolate the VCSEL sources 244 from
the one or more electrodes 246/247. In some embodiments of the system 200
of FIG. 2, the electrical-stimulation portions (electrodes 246/247 and
insulating sheath 245) and are omitted and only the optical-stimulation
portions are implemented. In some such embodiments, instead of using
electrodes 246 to stimulate the lower frequency range, one or more VCSEL
sources 244 located at the far apex end of substrate 243 are directed
into the apical end of cochlea 85 at angles sufficient to stimulate the
lower frequency range. In some embodiments, at least the
stimulation-emission end (the intra-cochlear portion 210 from which
optical and electrical-stimulation signals are emitted) of the cochlear
implant is implanted within, and along a length of, the scala tympani 89.
In other embodiments, at least the stimulation emission end of the
cochlear implant is implanted within, and along a length of, the scala
vestibuli 87. In some embodiments, the controller portion is external to
the cochlea, and a feed-through conduit goes through either the round
window and/or the oval window (depending on where the intra-cochlear
portion 210 is located) of the cochlea connecting the controller to the
intra-cochlear portion 210 (inside the scala tympani 89 and/or scala
vestibuli 87), wherein the feed-through conduit 248 is coated with a
bio-compatible material so that the round window and/or the oval window
membrane seals to the feed-through conduit 248. In other embodiments, the
entire implanted system 200 is within the scala tympani 89 or the scala
vestibuli 87, or even the scala media 86 of the cochlea 85.

[0121] In some embodiments, the one or more electrodes 246 at the apical
end of the implant are inserted to a location that is at least 50% of the
basal-to-apical length of the cochlear channel (whichever channel is used
for the implant) toward the apical end of the intra-cochlear portion 210
of the implant, as measured from the basilar membrane (i.e., the
electrodes are closer to the apical end than to the basal end of the
cochlea). In some embodiments, the one or more electrodes 246 at the
apical end of the implant are inserted to a location that is at least 75%
of the basal-apical length toward the apical end of the intra-cochlear
portion 210 of the implant (i.e., much closer to the apical end than to
the basal end). In some embodiments, the one or more electrodes 246 at
the apical end of the implant are inserted to a location that is at least
90% of the basal-apical length toward the apical end of the
intra-cochlear portion 210 of the implant (i.e., substantially at the
apical end).

[0122] In some embodiments, each of the VCSEL sources 244 is located on a
surface of substrate 243 that faces the organ of corti from inside
cochlea 85 (e.g., in some embodiments, substrate 243 extends inside the
scala tympani 89 (the lower channel) in cochlea 85 from near the base to
near the apex, such that each VCSEL array 244 emits light toward the
organ of corti 88). In some embodiments, no portion of system 200 is
inserted into the scala vestibuli channel 87 of cochlea 85. In some
embodiments, each VCSEL source 244 emits infrared optical-stimulation
signals.

[0123] In some embodiments, each VCSEL array 244 has a plurality of
emitters that emit light for one or more sensory frequency channels (each
sensory frequency channel being the nerve pathway from hair cells located
to respond to a particular audio frequency and to initial NAPs in one of
the auditory nerve pathways associated with that frequency). In some
embodiments, two rows of five VCSEL emitters extend across a width of
each VCSEL array 244, while in other embodiments, other numbers of rows
and other numbers of VCSEL emitters per row are provided. In some
embodiments, via testing and mapping after implantation, one or more of
the VCSEL emitters in one row is mapped and used to stimulate NAPs for
one sensory frequency channel, while one or more of the VCSEL emitters in
another row is mapped and used to stimulate NAPs for another sensory
frequency channel. In some embodiments, multiple VCSELs are provided in
each row (e.g., in some embodiments, many more than end up actually being
used) in order that, to accommodate placement errors, testing of all or
most of the stimulation sources, and then mapping of which stimulation
causes each of a plurality of sensory responses or perceptions so that
only the subset of stimulation sources that are most effective in causing
a response are used to generate NAPs based on the information content of
the audio signal. In some embodiments, VCSEL arrays that emit a plurality
of different wavelengths are used to customize the spatial absorption
profile of the stimulation light.

[0124] In some embodiments, each VCSEL source 244 includes a single VCSEL,
while in other embodiments, each VCSEL source 244 includes a plurality of
individually activatable lasers oriented to emit light along
substantially parallel axes with somewhat overlapping spots of
illumination (such that, in some embodiments, one or more of the group of
VCSELs can be individually activated at a succession of different times
after implantation, in order to dynamically determine which of the
plurality of VCSELs in a single array 244 is best suited to stimulate one
or more nerves that are very near to one another, but for which it is
desired to selectively stimulate•one or more individually without
stimulating the adjacent neighboring nerves). In other embodiments, each
group of VCSELs 244 is configured to emit laser-light beams in a
plurality of non-parallel directions to stimulate nerves that are not
right next to one another. In some embodiments, each group of VCSELs 244
has an associated one or more focussing devices to focus the light (e.g.,
graded-index-fiber (GRIN) lenses, diffraction gratings or holographs, or
other suitable microlenses that either disperse the light, in some
embodiments, or in other embodiments focus the light to a small spot of
excitable tissue such as hair cells in cochlea 85 or spiral ganglion
cells (SGCs)), while in other embodiments, no lenses are used. In some
embodiments, a plurality of channels (e.g., two to a hundred or more
channels) each has one or more VCSELs (e.g., in some embodiments, 1 to 5
to more VCSELs per channel), such that one or more of the VCSELs on a
given channel can be selectively activated to stimulate nerves associated
with that channel. In some embodiments, a plurality of VCSELs are each
activated to trigger NAPs in additional neighboring spiral ganglion
cells, and/or to increase the pulse-repetition rate of NAPs in a
particular set of nerve pathways in order to provide loudness control, as
mentioned earlier. In some embodiments, each VCSEL is connected to two
electrical conductors (namely, its individual signal conductor and a
common or ground conductor that is shared with other VCSEL emitters). In
some embodiments, an array of VCSELs is arranged such that all VCSELs in
any one row share an anode connection and all VCSELs in any one column
share a cathode connection, and such that each VCSEL emitter is uniquely
addressed by electrically driving its row anode and its column cathode
(of course, the terms row and column can be interchanged).

[0125] In some embodiments, the implanted device of the present invention
includes a sound sensor (microphone; not shown) that, upon activation by
an external sound (pressure wave), generates one or more electrical
signals. In some embodiments, a computerized sound analyzer decomposes
the audio signal (e.g., using a fast Fourier transform (FFT), discrete
cosine transform (DCT), or other suitable digital signal processor (DSP)
or analog means) to output time-varying frequency components. In some
embodiments, the optical-stimulation signals from VCSEL arrays 244 and
electrical-stimulation signals are generated based on the outputted
time-varying frequency components signals.

[0126] FIG. 2B is a perspective view of VCSEL-based stimulation system 200
showing a cut-away view of cochlea 85. In some embodiments, system 200
includes a plurality of VCSEL sources 244 configured to direct optically
stimulating light pulses to excitable tissue in the cochlea of a person
in order to trigger nerve action potentials in the auditory nerve 91 of
the person. In some embodiments, system 200 includes a first electrode
246A and a second electrode 246B located deep in the apical end of
cochlea 85. In some such embodiments, electrodes 246A and 246B are
electrically isolated from each other by insulating sheaths 245. In some
embodiments, system 200 is configured to optically stimulate auditory
nerve 91 by directing a plurality of pulsed light signals at one or more
locations on the organ of corti 88. In other embodiments, system 200 is
configured to optically stimulate auditory nerve 91 by directing a
plurality of pulsed light signals at one or more nerves 98 that are
located in the pathway between the organ of corti 88 and the auditory
nerve 91. For example, in some embodiments, VCSEL source 244A directs a
pulsed laser beam 84A at a first location of one or more nerves 98 and
VCSEL source 244B directs a pulsed laser beam 84B at a second location of
one or more nerves 98.

[0127] FIG. 2C is a schematic perspective exploded-view diagram
illustrating light-emitting, light-focussing, and/or light-pointing
device 205, used to implement some embodiments of VCSEL emitters 244 of
FIG. 2B. In some embodiments, each device 205 includes a semiconductor
chip 252 having plurality of VCSELs 251 arranged in an array (e.g., in
some embodiments, a Cartesian grid, while in other embodiments, any other
suitable pattern) that allows a large number of VCSELs to be implanted
such that each directs its light to a slightly different location, and
such that a much smaller number of the VCSELs is activated at any one
time (e.g., in some embodiments, some VCSELs may never be activated
except during testing, calibration and customization, while others may be
used more or less frequently depending on whether their neighboring
VCSELs are activated to emit stimulation light or have recently been
activated). In some embodiments, an array or other structure of focussing
elements 254 (e.g., microlenses, holographs, GRIN lenses or the like)
and/or angle-pointing elements 256 (e.g., a plurality of prisms (as shown
in FIG. 2C), gratings, MEMS mirrors, or the like) are provided to focus,
and/or point the stimulation light in various angular directions, towards
the nerves to be stimulated. In some embodiments, a plurality of such
light-emitting devices 205 is used as the light-source elements 244 of
FIG. 2A and FIG. 2B affixed along the length of ribbon 212. In some such
embodiments, ribbon 212 includes a plurality of electrical connections
arranged to multiplex signals to independently activate selected ones of
the VCSELs, and optionally includes a high-thermal-conductivity material
configured to remove excess device heat from within the cochlea. In some
embodiments, ribbon 212 further includes one or more thermal sensors
(e.g., in some embodiments, implemented on the light-emitting device 205,
while in other embodiments, implemented on separate devices also located
along ribbon 212) that transmit temperature-indicating signals from the
cochlea to controller 250.

[0128] FIG. 3M includes a schematic graph 300 of the tissue absorption 302
(which is one indication of the sensitivity to stimulation light) of a
tissue at various wavelengths in a given range, and a superimposed graph
301 of a power-source spectrum having different amounts of power at each
of a plurality of wavelengths, which has been customized to provide a
desired spatial heating profile due to absorption of infrared light
having the various wavelengths. In some embodiments of the present
invention as shown in any of the figures herein, the range of wavelengths
in the power-source spectrum is at least 2.5 nm. In some embodiments, the
range of wavelengths in the power-source spectrum is at least 5 nm. In
some embodiments, the range of wavelengths in the power-source spectrum
is between about 5 nm and about 10 nm. In some embodiments, the range of
wavelengths in the power-source spectrum is between about 10 nm and about
15 nm. In some embodiments, the range of wavelengths in the power-source
spectrum is between about 15 nm and about least 20 nm. In some
embodiments, the range of wavelengths in the power-source spectrum is
between about 20 nm and about 30 nm. In some embodiments, the range of
wavelengths in the power-source spectrum is between about 30 nm and about
40 nm. In some embodiments, the range of wavelengths in the power-source
spectrum is more than 40 nm.

[0129] In some embodiments, the wavelengths of the optical power source
are in the range of about 800-900 nm. In some embodiments, the
wavelengths of the optical power source are in the range of about
900-1000 nm. In some embodiments, the wavelengths of the optical power
source are in the range of about 1000-1100 nm. In some embodiments, the
wavelengths of the optical power source are in the range of about
1100-1200 nm. In some embodiments, the wavelengths of the optical power
source are in the range of about 1200-1300 nm. In some embodiments, the
wavelengths of the optical power source are in the range of about
1300-1400 nm. In some embodiments, the wavelengths of the optical power
source are in the range of about 1400-1500 nm. In some embodiments, the
wavelengths of the optical power source are in the range of about
1500-1600 nm. In some embodiments, the wavelengths of the optical power
source are in the range of about 1600-1700 nm. In some embodiments, the
wavelengths of the optical power source are in the range of about
1700-1800 nm. In some embodiments, the wavelengths of the optical power
source are in the range of about 1800-1900 nm (in some embodiments, this
is a more preferred range). In some embodiments, the wavelengths of the
optical power source are in the range of about 1900-2000 nm. In some
embodiments, the wavelengths of the optical power source are in the range
of about 2000-2100 nm. In other embodiments, the wavelengths of the
optical power source extend across (include two or more different
wavelengths within (i.e., two or more spectrally separated wavelengths
within)) one or more of these ranges.

[0130] In some embodiments, within the selected range of stimulation
wavelengths, the tissue-absorption value increases as the wavelength
increases (as shown by graph 302 of FIG. 3M and graph 307A of FIG. 3B)
and the optical-stimulation power at each of a plurality of wavelengths
decreases as the wavelength increases (as shown by graph 301 of FIG. 3M,
graph 308A of FIG. 3D, and graph 309A of FIG. 3F). In other embodiments,
within the selected range of stimulation wavelengths, the
tissue-absorption value decreases as the wavelength increases (as shown
by graph 307B of FIG. 3G and graphs 307D and 307C of FIG. 3J) and the
optical-stimulation power at each of a plurality of wavelengths increases
as the wavelength increases (as shown by graph 308B of FIG. 3H and graph
309B of FIG. 3I).

[0131] FIG. 3A is a conceptual schematic diagram of a broadband wavelength
source 310 having a designed power/wavelength spectrum profile formed to
customize the absorption of optical power in the tissue of interest. In
some embodiments, broadband wavelength source 310 includes a laser having
a reflective grating or other means for generating different amounts of
light output at various wavelengths (such as shown in FIG. 3D described
below). Source 310 is controlled by an electrical signal 317 to emit
pulsed light 318 having a spectrum such as shown in FIG. 3D, FIG. 3H, or
FIG. 3K, as desired by the designer. In some embodiments, the wavelength
range (e.g., full-width half-maximum (FWHM) range of wavelengths) of the
optical-source power spectrum is at least 2.5 nm. In some embodiments,
the range of wavelengths in the optical-source power spectrum is at least
5 nm. In some embodiments, the range of wavelengths in the optical-source
power spectrum is between about 5 nm and about 10 nm. In some
embodiments, the range of wavelengths in the optical-source power
spectrum is at least about 10 nm wide and less than about 100 nm (in some
embodiments, this is a preferred range). In some embodiments, the range
of wavelengths in the optical-source power spectrum is between about 10
nm and about 15 nm. In some embodiments, the range of wavelengths in the
optical-source power spectrum is between about 15 nm and about least 20
nm. In some embodiments, the range of wavelengths in the optical-source
power spectrum is between about 20 nm and about 30 nm. In some
embodiments, the range of wavelengths in the optical-source power
spectrum is between about 30 nm and about 40 nm. In some embodiments, the
range of wavelengths in the optical-source power spectrum is more than 40
nm. In some embodiments, the optical-stimulation signal includes two or
more different wavelengths within (i.e., two or more spectrally separated
wavelengths within) one or more of these ranges.

[0132] FIG. 3B includes a schematic graph 307A of a tissue sensitivity to
optical stimulation for a first given type or composition of tissue as a
function of the wavelength of the optical stimulation. In some
embodiments, graph 307A is representative of light absorption at various
wavelengths. Note that in some wavelength ranges the sensitivity will
increase at longer wavelengths such as shown in FIG. 3B, while in other
embodiments, the sensitivity will decrease at longer wavelengths such as
shown in FIG. 3G, while in still other embodiments, the sensitivity peak
at different wavelengths for different tissue types, such as shown in
FIG. 3J, as described below.

[0133]FIG. 3C is a schematic diagram of a broadband wavelength source 320
having a designed power/wavelength spectrum profile formed to customize
the absorption of optical power in the tissue of interest. In some
embodiments, source 320 includes a conventional broadband source 321
having a broad Gaussian linewidth (e.g., a laser (such as a
vertical-cavity surface-emitting laser (VCSEL) or optically-pumped fiber
laser) or superluminescent light-emitting diode or filtered amplified
spontaneous emission (ASE) fiber source) which is controlled by
electrical signal 327 to emit pulsed light 322. The pulsed light passes
through a shaped-spectrum filter 323 such that output of the broadband
wavelength source 320 emits pulsed light 328 having a spectrum such as
shown in FIG. 3D, FIG. 3H, or FIG. 3K, as desired by the designer.

[0134] FIG. 3D is a schematic graph 308A of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue.

[0135] FIG. 3E is a schematic diagram of a broadband wavelength source 330
having a designed power/wavelength spectrum profile formed to customize
the absorption of optical power in a tissue of interest. In some
embodiments, the power spectrum is designed to compensate for the shape
of the tissue absorption characteristics (such as shown in FIG. 3B), in
order to obtain the desired heat profile (such as shown in FIG. 4D
(showing activation of NAPs substantially equally at different depths) or
as shown in FIG. 4E (showing activation of NAPs differently at different
depths)). In some embodiments, a plurality of narrow-band lasers 331 are
controlled by a plurality of independent electrical signals 337.1, 337.2,
. . . 337.N, such that the power at each laser wavelength can be varied,
and when the outputs of the individual lasers are combined with a beam
combiner 334, the broadband wavelength source 330 has an output beam 339
having a spectrum such as shown in FIG. 3F, or as desired by the
designer. In some embodiments, the plurality of narrow-band lasers 331
are controlled by a plurality of independent electrical signals 337.1,
337.2, . . . 337.N, such that the power at each laser wavelength can be
varied over time with different waveshapes and/or pulses at different
times, resulting in spectra that vary over time such as shown in FIGS.
4F, 4G, and 4H described below.

[0136] FIG. 3F is a schematic graph 309A of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
tissue. In some embodiments, the power/wavelength spectrum profile of
graph 309A is obtained by combining a plurality of light signals from a
plurality of narrow-band lasers 331.

[0137] FIG. 3G is a schematic graph 307B of a tissue sensitivity to
optical stimulation for a second given type or composition of tissue as a
function of the wavelength of the optical stimulation. In contrast to the
chosen tissue type and wavelength range shown in FIG. 3B above, this
tissue type has decreased sensitivity (e.g., due to decreased absorption)
at longer wavelengths.

[0138] FIG. 3H is a schematic graph 308B of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in the
tissue having the sensitivity of the graph 307B of FIG. 3G.

[0139] FIG. 3I is a schematic graph 309B of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
tissue. In some embodiments, the power/wavelength spectrum profile of
graph 309B is obtained by a device such as shown in FIG. 3E described
above.

[0140] FIG. 3J includes schematic graphs 307C, 307D, and 307E of tissue
sensitivity to optical stimulation for a three types or compositions of
tissue as a function of the wavelength of the optical stimulation. For a
group of such tissue types, it is sometimes desirable to have some of the
tissues (e.g., those of graphs 307D and 307E) absorb the stimulation
light and be heated enough to trigger NAPs, while having some others of
the tissues (e.g., those of graph 307C) not absorb enough energy to
trigger NAPs.

[0141] FIG. 3K is a schematic graph 308C of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
plurality of tissues. Such a broad spectrum is useful in cases when it is
desired to trigger NAPs in all the tissue types of the graphs of FIG. 3J.

[0142] FIG. 3L is a schematic graph 309C of a designed power/wavelength
spectrum profile used to customize the absorption of optical power in a
plurality of tissues. Such a selectively activated spectrum is useful in
cases when it is desired to trigger NAPs in some of the tissues (e.g.,
those of graphs 307D and 307E of FIG. 3J), while having some others of
the tissues (e.g., those of graph 307C) not absorb enough energy to
trigger NAPs.

[0143] FIG. 4 is a plot 400 of a temperature profile of tissue due to
absorption of infrared light from a single-wavelength source. In this
plot, the tissue vertically in the center and horizontally at the left
(in an innermost ring) is heated to (e.g., in this example) to 42°
C. (42 degrees centigrade), which in some embodiments, is sufficient to
trigger a NAP if a nerve were located at that position. The tissue to the
right of a tissue depth of 2 mm remains at 37.5° C. (normal body
temperature), while intermediate tissue is heated, but not enough to
trigger NAPs even if nerves were located there.

[0144] FIG. 4A is a schematic diagram that includes a hypothetical plot
440 of a temperature profile of tissue due to absorption of light from
single-wavelength source 331 of infrared light having a first wavelength.
The oval lines represent equi-temperature locations, with line 446
representing the tissue area having the highest temperature (this would
be the temperature needed to trigger NAPs in nerves, since the controller
will strive to prevent stimulation signals that result in higher
temperature, since those are not more effective at triggering NAPs and
are likely to damage tissue). Each of the other equi-temperature lines
(lines 445, 444, 443, 442 and 441) represent successively lower
temperatures, each of which is too low to trigger NAPs. Of the nerves 81,
82, and 83 in the tissue 80, only the nerve 81 is located within the 446
line, and so it, but not the others, will have a NAP triggered.

[0145] FIG. 4B is a schematic diagram that includes a plot 440 of a
temperature profile of tissue due to absorption of single-wavelength
source 332 of infrared light having a second wavelength. Again, the oval
lines represent equi-temperature locations, with line 446 representing
the tissue area having the temperature needed to trigger NAPs in nerves.
Of the nerves 81, 82, and 83 in the tissue 80, only the nerve 82 is
located within this 446 line, and so it, but not the others, will have a
NAP triggered.

[0146] FIG. 4C is a schematic diagram that includes a plot 440 of a
temperature profile of tissue due to absorption of single-wavelength
source 333 of infrared light having a third wavelength. Again, the oval
lines represent equi-temperature locations, with line 446 representing
the tissue area having the temperature needed to trigger NAPs in nerves.
Of the nerves 81, 82, and 83 in the tissue 80, only the nerve 83 is
located within this 446 line, and so it, but not the others, will have a
NAP triggered. In some embodiments, the threshold optical-stimulation
signal extends across two of the three cases shown in FIG. 4A, FIG. 4B or
FIG. 4C.

[0147] FIG. 4D is a schematic diagram that includes a plot 440 of a
temperature profile of tissue due to absorption of source 330A of
infrared light having a customized spectrum of wavelengths (e.g., the
spectrum of FIG. 3D, 3F, or 3K). Note that line 446 representing the
tissue area having the temperature needed to trigger NAPs in nerves is
larger than previous cases of FIG. 4A, FIG. 4B or FIG. 4C (extending from
shallow to deep), and now covers all three of the nerves 81, 82, and 83
in the tissue 80, so all the nerves 81, 82, and 83, each at a different
depth, have a NAP triggered.

[0148]FIG. 4E is a schematic diagram that includes a plot 440 of a
temperature profile of tissue due to absorption of infrared light from
source 330B having a customized spectrum of wavelengths (e.g., the
spectrum of FIG. 3L). Note that line 446 of FIG. 4D representing the
tissue area having the temperature needed to trigger NAPs in nerves is
now split into two parts (both of which trigger a NAP), 446S which covers
the shallow nerve 81, and 446D which covers deep nerve 83, but this
threshold region does not cover middle nerve 82 in the tissue 80, so the
moderate-depth nerve 82 will not have a NAP triggered. In some
embodiments, wavelengths of the spectrum are chosen such that part (some
of the wavelength(s)) of the stimulation optical signal are absorbed at a
shallow depth (to provide the triggering temperature labeled 446S) and
part (others of the wavelength(s)) of the stimulation optical signal is
absorbed at a deep depth (to provide the triggering temperature labeled
446D).

[0149] FIG. 4F is a schematic graph 409A of a designed power/wavelength
spectrum profile for a time period N in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues.

[0150] FIG. 4G is a schematic graph 409B of a designed power/wavelength
spectrum profile for a time period N+1 in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues.

[0151] FIG. 4H is a schematic graph 409C of a designed power/wavelength
spectrum profile for a time period N+2 in a sequence of time periods N,
N+1, N+2 used to customize the temporal absorption of optical power in a
plurality of tissues. The time-varying sequence of different power
spectra is used, in some embodiments, to customize the triggering of
NAPs.

[0152] FIG. 5 is a block diagram of an implantable/partially implantable
system 500 that uses a VCSEL array for light stimulation of the auditory
nerve of a person. System 500 represents one embodiment of the present
invention, wherein a low-power, low-threshold VCSEL array 501 (e.g., a
plurality of VCSEL sources such as found in system 200 shown in FIG. 2A
and FIG. 2B, and device 205 of FIG. 2C) emits laser light from each of a
plurality of VCSELs, for example VCSELs implemented as an array of
separately activatable lasers formed in a monolithic semiconductor chip.
In some embodiments, each laser beam is separately controlled by
laser-and-power controller 510 that drives the laser-diode VCSELs under
control of a processor or circuitry 509 that generates signals that are
configured to stimulate the tissue in response to input audio signals as
desired. In some embodiments, the drive signals are transmitted to VCSEL
array 501 via electrical connection 580. In some embodiments, system 500
includes wireless transceiver 71 (e.g., from a system console 100 such as
shown in FIG. 1) that allows wireless control and customization
programming of system 500 (via transceiver 511) and/or an externally worn
device 111. In some embodiments, externally worn device 111 includes one
or more microphones or similar sound sensors, audio-processing circuitry,
and a wireless transmitter to send the processed audio signals to
transceiver 511 in the intra-cochlear portion of 200 shown in FIG. 5. In
some such embodiments, externally worn device 111 includes one or more
rechargeable batteries (which may be recharged overnight in a recharging
station while the patient sleeps) and a wireless power transducer to send
electrical power to device 500. In other embodiments, implant 500
includes one or more microphones or similar sound sensors in the set of
sensors 508 such that the implant is self contained (in some such
embodiments, implant 500 itself includes one or more rechargeable
batteries 507 that may be recharged overnight by a nearby wireless
recharging station (which, in some embodiments, is included in wireless
transceiver 71) while the patient sleeps.

[0153] In some embodiments, the set of sensors 508 includes one or more
temperature sensors, located in and/or along the in-body portion 589
implanted within the cochlea, and configured to provide feedback to
system 500 in order to provide a safety shutdown and/or optimize the
optical stimulation provided by system 500. In some embodiments, at least
one temperature sensor in the set of sensors 508 is implemented in each
of a plurality of VCSEL-array chips 501 to allow temperature monitoring
throughout the cochlea.

[0154] In some embodiments, long-wavelength VCSEL devices (e.g., VCSELs
having wavelengths in the range of 1.6 to 2 microns) and/or VCSEL arrays,
such as described in U.S. Pat. No. 7,031,363 to Biard and U.S. Pat. No.
7,004,645 to Lemoff (which are each incorporated herein by reference),
are used for each of a plurality of VCSEL arrays 501.

[0155] With VCSEL emitters as small as about ten (10) microns (or smaller)
in diameter per channel, in some embodiments, a single VCSEL chip or
assembly is used to output multiple independent stimulation channels
(VCSEL laser signals) in any suitable array permutation or shape, and in
some embodiments, these channels are fiber coupled, lens coupled, and/or
direct light straight to a plurality of areas of tissue. In some
embodiments, a combination of both fiber-coupled and direct propagation
laser output is used to stimulate tissue. In some embodiments, the VCSELS
are located in device 504 outside the cochlea and optical fibers are used
to fiber-couple the light to the various areas inside the cochlea.

[0156] In some embodiments, implantable/partially implantable system 500
includes an electrical-stimulation driver 520 to drive electrodes
contained within the implantable part of the system, 200. The drive
signals are transmitted to the electrodes via electrical connection 522.
In some embodiments, these electrodes stimulate auditory nerves in the
person to improve low-frequency hearing response.

[0157] FIG. 6A is a flowchart of a method 601, according to some
embodiments of the present invention, where the method is performed by a
programmed information processor using stored instructions on
non-transitory computer readable medium 690. The method 601 employs,
depending on the embodiment of the invention, a plurality of collections
of externally provided data stored in computer-readable data structures.
In some embodiments, data includes patient-specific audio information, or
auditory profile 685. In some embodiments, data includes general rules
for mapping sounds from the environment onto auditory-nerve stimulators
684. In some embodiments, the data includes anti-tissue-damage rules 682,
which, in some embodiments, includes rules based on tissue heating. In
some embodiments, data includes anti-device-damage rules 681, which, in
some embodiments, includes rules based on tissue heating. In some
embodiments, data includes pulse shaping rules 683.

[0158] In some embodiments, audio sensors, which include one or more
microphones 610, detect sounds in the environment around a patient (a
person) wearing the implantable or partially implantable
auditory-nerve-stimulation system (cochlear implant). Signals are sent to
an audio processor where real-time audio data is extracted from the
signals (function 612). In some embodiments, input signal audio data is
organized into frames, where a given frame contains information about the
input signal at a given point in time. In some embodiments, this
necessary information includes the audio spectrum of the input signal. In
some embodiments, an auditory channel map is produced (function 620). In
some embodiments, general auditory mapping rules 684 and/or a patient
specific auditory profile 685 are used to produce the auditory channel
map. The auditory channel map is stored into computer-readable data
structures 621. In some embodiments, auditory channels are organized into
a plurality of bins, where each bin is a set of frequency-adjacent
auditory channels. The data extracted from the input signal is processed
into channels (function 622), using the stored auditory channel map 621,
by determining the loudness (signal strength) of the portion of the input
signal that corresponds to each channel. This channel information is
stored (function 624) for each channel in computer-readable data
structures 686. In some embodiments, the information stored in the
computer readable data structures 686 includes historic channel
information, that is, the audio information from some number of previous
points in time. In some embodiments, where the input audio signal is
organized into frames, channel information is stored for a
designer-determined number of frames, for each of a plurality of
frequencies or frequency bands. The time-based (historic) channel
information provides the operational data needed to restrict the
operation of specific light emitters to limit potential nerve damage in
the cochlea, or light-emitter (e.g., VCSEL) damage (e.g., damage that
might occur due to accumulated heat from too many pulses to one area of
the cochlea within a given amount of time (e.g., in some embodiments, the
most recent one-second time period, for example) as re-measured on an
on-going basis; or too many pulses from one VCSEL emitter in such a
period of time). An example of a graph of one frame of information is
shown in 687. In some embodiments, if the accumulated light signal from a
particular received audio frequency would cause too much heat in one area
of the cochlea or one VCSEL, the pulse rate to that one area of the
cochlea or one VCSEL is reduced relative to normal pulse rate for a
particular loudness in the received audio frequency band. In some such
embodiments, the pulses of a frequency that is one octave above or below
the received audio frequency band are increased to provide a substitute
that can be perceived or understood by the patient to convey similar
information as would have been conveyed by pulses at the normal rate for
the cochlear area normally stimulated by the received audio
frequency-band signal. In other words, if one particular received audio
frequency band receives too much signal in a given time period, the
cochlear stimulation for that frequency is reduced and/or the stimulation
is instead applied to one or more other cochlear regions that is/are an
integer number of octaves away from the cochlear region normally
stimulated for that received audio frequency or frequency band.

[0159] The channel information is processed (function 630) to generate
drive control signals for the VCSELs. The VCSELs are driven (function
695) such that the optical signals emitted from the VCSELs stimulate
auditory nerves in the person wearing the cochlear implant so that the
person perceives the audio signal detected by the microphones (or other
audio-sensing devices). Light (the optical signal) emitted by a given
VCSEL stimulates a specific auditory nerve or nerves. Each specific
auditory nerve corresponds to a particular sound frequency, and the
triggering of that auditory nerve results in the person perceiving sound
of that corresponding frequency. In some embodiments, the output of the
VCSELs is pulsed. In some embodiments, the intensity of the optical
signal emitted from the VCSELs is varied in order to produce the
perception of differing loudness levels. In other embodiments, the VCSELs
are pulsed at varying rates such that the person to perceives differing
loudness levels.

[0160] In some embodiments, additional information is used in the
processing step 630 which can include, but is not limited to, heat-based
VCSEL-anti-device damage rules 681, heat-based tissue-anti-damage rules
682, pulse-shaping rules 683, history of recent audio signals 686, and
nerve response feedback information 619. Heat-based VCSEL-anti-device
damage rules 681 may be used to limit how long, at what power level, and
how frequently a specific VCSEL is operated, in order to prevent damage
to the VCSEL from overheating. Heat-based tissue-anti-damage rules 682
may be used to limit how long, at what power level, and how frequently a
specific auditory nerve and/or surrounding tissue is illuminated, in
order to prevent damage to the nerve and tissue from overheating. In some
embodiments, where the channels are organized into bins, the
tissue-anti-damage rules and the VCSEL-anti-device damage rules are
applied within each bin (set of adjacent frequency channels). In some
embodiments, the rules can include limits as to the number of VCSELs
operated in a given bin at a single point in time or within a window of
time.

[0161] In some embodiments, the optical signal 696 emitted from the VCSELs
is transmitted (function 697) to the auditory nerves, stimulating the
nerves by triggering NAPs in the nerves (function 698). In some
embodiments, optical detectors sense the nerve response (function 618),
and the nerve responses are processed (function 619) to determine how the
person's auditory nerves responded to the optical-stimulation signals. In
some embodiments, the response information is fed back to the
channel-information-processing function 630, where this response
information is used to improve the channel processing and the driving of
the VCSELs in order to improve the sound perceived by the person wearing
the cochlear implant.

[0162] In some embodiments, the programmed information-processor-stored
instructions and the various computer-readable data structures used by
the instructions, which are described above, are received (via function
691 of FIG. 6A) from an external reprogramming device, allowing the
operation of the cochlear implant to be altered after the
auditory-nerve-stimulation system has been implanted in a person.

[0163] Referring again to FIG. 6A, in some embodiments of method 601, at
block 610 an audio signal is obtained from one or more microphones
configured to obtain signals representing sounds and pressure variations
in the environment surrounding the patient, and to generate electrical
signals that are processed by process 612 to obtain real-time data
representing each of a plurality of audio-frequency channels, each
audio-frequency channel signal having a value based on the sounds within
a limited band of audio frequencies for the current time frame (or
processing cycle). In some embodiments, the loudness values for the
various audio-frequency channels are processed by process 622 to select
which audio-frequency channels will be activated within each of a
plurality of bins of audio-frequency channels, and a history of such
values is stored by process 624 into data structure 686 (schematically
shown in the adjacent graph 687 of audio-frequency channel values,
wherein graph 687 shows power of each audio-frequency channel on the
vertical axis and center frequency of each audio-frequency channel on the
horizontal axis). In some embodiments, experimental rules for auditory
stimulation are derived and a storage-medium having a general-rule
computer-readable data structure (CRDS) 684 contains general rules for
mapping audio input to auditory stimulation based on physiological
considerations. In addition, some embodiments include a patient-specific
CRDS 685 that modifies or supplements the general-rule CRDS 684. In some
embodiments, patient-specific CRDS 685 is derived by empirically
outputting a set of audio output signals to the implanted system and
eliciting and receiving feedback from the patient indicative of the
sensations perceived as a result of the optical and/or electrical
stimulation applied. In some embodiments, operation 620, based on
general-rule CRDS 684 and patient-specific CRDS 685, derives a map of
auditory input (e.g., frequencies)-to-stimulation site(s) based on
empirical testing and stores the resulting map into map CRDS 621. In some
embodiments, for each successive time frame, operation 622 combines the
audio-frequency channel-loudness-signal values from audio-processing
operation 612 and the mapping rules from CRDS 621 into audio-frequency
channel-stimulation values. In some embodiments, operation 624 stores
into CRDS 686 a history of the audio-frequency channel and/or bin values
for most-recent P frames. Operation 630 then takes the audio-frequency
channel information for the current time frame (and optionally from a
predetermined number of prior time frames) and, using the heat-based
anti-tissue-damage-rules CRDS 682 (which limit the number of
audio-frequency channels that are allowed to be activated in any one time
frame and/or within P successive time frames), along with data from VCSEL
heat-based anti-device-damage-rules CRDS 681 and rules for stimulation
pulse shapes (pulse width and/or rise/fall shape) in CRDS 683, operation
630 generates pulse parameters for the stimulation light for each VCSEL
to be activated. Operation 695 takes the pulse parameters from operation
630 and drives the VCSELs to emit stimulation signals (a set of infrared
optical-stimulation signal pulses and optionally one or more electrical
stimulation pulses) which are transmitted (function 697) to the tissue to
trigger CNAPs. In some embodiments, the resulting physiological response
is a set of CNAPs 698 that is transmitted to the brain of the patient,
and operation 618 optionally measures the nerve response and operation
619 processes a feedback signal that is fed back into operation 630. In
some embodiments, a reloadable computer-readable storage medium 690 holds
instructions and data structures (in some embodiments, received (e.g., by
a wireless receiver) 691 from an external device) that control the
operations described above.

[0164] FIG. 6B is a flow chart of a method 602, according to some
embodiments of the present invention, for optimizing the pulse-repetition
rate used during optical stimulation of the cochlea. In some embodiments,
pulsed light signals are generated at block 650, the generated light
signals are delivered to excitable tissue in a cochlea of a person to
optically stimulate the tissue such that NAPs are triggered at block 652,
feedback is elicited and received during (or shortly after) the delivery
of the signals at block 654, the delivery of the signals is empirically
tested (to try to find the most effective pulse parameters) at block 656,
(the above-listed operations are iteratively repeated 662 in some
embodiments), the most effective pulse-repetition rate for optical
stimulation is determined at block 658, and later, at block 660, during
normal operation the signals are delivered to the excitable tissue based
on the pulse-repetition rate(s) determined to be most effective. In some
embodiments, the normal operation of the device uses the different rates
that are determined to be most effective for different frequency ranges
(i.e., each audio-frequency channel or bin has its own most-effective
rate determined, stored and later used) or sound types (e.g., speech
versus music).

[0165] FIG. 7 is a flow chart of a method 700, according to some
embodiments of the present invention. The upper portion of this method
700 is similar to method 602 of FIG. 6B, except that the test sounds are
customized to improve the patient's enjoyment of music. Again, in some
embodiments, pulsed light signals are generated at block 650 (now based
on semitone musical notes or other suitable sounds for music), the
generated light signals are delivered to excitable tissue in a cochlea of
a person to optically stimulate the tissue such that NAPs are triggered
at block 652, feedback is elicited and received during (or shortly after)
the delivery of the signals at block 654, the delivery of the signals is
empirically tested for effectiveness in providing semitone sensations at
block 656, (the above-listed operations are iteratively repeated 662 in
some embodiments). At block 730, the most effective one or more VCSELs
for optical stimulation are determined, and later during normal operation
at block 735, the signals are delivered to the specific areas excitable
tissue from the selected VCSELs based on the VCSELs determined to be most
effective for semitones or other musical features (e.g., many different
frequencies for snare drum sounds). In some embodiments, different
locations are most effective for different musical types (i.e., each
musical type may benefit from selecting VCSEL channels (i.e., selecting
from among the set of all optical-stimulation channels) for each music
feature differently; these maps of music-to-VCSEL mappings are stored and
later used). In some embodiments, each audio-frequency channel uses one
or more optical-stimulation channels (i.e., one or more emitters that
stimulate a corresponding number of areas of the cochlea) to create a
perceived sound sensation associated with the frequencies within the
audio-frequency channel. In some embodiments, a large number of emitters
are implemented in the implanted device and the calibration process
selects, from among the total available emitters, one or more of those
that are best suited for a particular hearing environment (e.g., speech
versus music listening), and that are then to be used for each of the
plurality of perceived sound sensations of that environment.

[0166] FIG. 8A is a flow chart of a method 800, according to some
embodiments of the present invention. Method 800 is described below.

[0167] FIG. 8B is a graph of a binned-channel-with-history spectrum 802,
according to some embodiments of the present invention. This graph shows
a plurality of audio-frequency channels having current power levels 824
and an indication of recently-past power levels 825. Each one of the
plurality of audio-frequency channels is also assigned into one or more
bins 812.1-821.N--in the embodiment shown the bins include a plurality of
overlapping bins (note that the right-most two audio-frequency channels
of bin 812.1 are the left-most two channels of bin 812.2, and so on).

[0168] Referring to FIG. 8A, at block 805, an audio signal having an audio
spectrum is obtained. At block 810, the audio signal is processed into M
audio-frequency channels for each of a plurality of successive time
frames. At block 815, a subset of up to N audio-frequency channels are
selected from the original M channels for the current time frame, based
on how many audio-frequency channels are the most active in each bin and
optionally how many of those channels or of nearby channels were
activated in the recent past. At block 820, one or more pulses of
optical-stimulation light are generated for each of the selected N
channels active for this time frame. At block 825, the light is delivered
to the excitable tissue.

[0169] FIG. 9 is a flow chart of a method 900, according to some
embodiments of the present invention. The upper portion of this method
900 is similar to method 602 of FIG. 6B, except that the test
optical-stimulation parameters are customized to improve the
effectiveness of various values to provide a sensation of loudness having
an increased dynamic range and/or to achieve some other hearing or
comfort goal. Again, in some embodiments, pulsed light signals are
generated at block 650 (now having a parameter such as optical spectrum,
pulse power, or other parameter being varied), the generated light
signals are delivered to excitable tissue in a cochlea of a person to
optically stimulate the tissue such that NAPs are triggered at block 652,
feedback is elicited and received during (or shortly after) the delivery
of the signals at block 654, the delivery of the signals is empirically
tested at block 656 for effectiveness in providing a sensation of
loudness having an increased dynamic range and/or achieving some other
hearing or comfort goal, (the above-listed operations are iteratively
repeated 662 in some embodiments). In some embodiments, the empirical
testing 656 determines a plurality of parameters that are, as a whole,
most effective (e.g., sometimes this produces a compromise between
parameters that need to be different for different environments). At
block 925, the most effective parameter(s) for optical stimulation are
determined, and later during normal operation at block 930, the
optical-stimulation signals are generated using the parameter(s)
determined here to be most effective for delivering the hearing
perception desired. In some embodiments, different parameters are most
effective for different speech or musical types (i.e., each musical type
may benefit from selecting a different set of parameters, and these
mappings are stored and later used).

[0170] FIG. 10 is a flow chart of a method 1000, according to some
embodiments of the present invention. The upper portion of this method
1000 is similar to method 602 of FIG. 6B, except that the test sets a
peak power and a repetition rate at preset values and varies the
pulse-width optical-stimulation parameter (and thus varies the energy
amount of each pulse) in order to improve the effectiveness of various
pulse-width values to provide improved perceived dynamic range of
loudness. Again, in some embodiments, pulsed light signals are generated
at block 650 (now having a parameter such as pulse width being varied),
the generated light signals are delivered to excitable tissue in a
cochlea of a person to optically stimulate the tissue such that NAPs are
triggered at block 652, feedback is elicited and received during (or
shortly after) the delivery of the signals at block 654, at block 1020,
the pulse width is varied while maintaining peak power and repetition
rate fixed, and the effectiveness of various different pulse widths to
give different loudness perception is empirically tested at block 1025,
(the above-listed operations are iteratively repeated 662 in some
embodiments). At block 1025, the signals are delivered and at block 1030
the most effective parameter(s) for optical stimulation are determined,
and later during normal operation at block 1035, the optical-stimulation
signals are generated using the parameter(s) determined here to be most
effective for delivering the hearing perception desired.

[0171]FIG. 11 is a diagram the firing of auditory nerve cells 1100 as
hair cells are deflected. In some embodiments of the present invention,
perceived loudness of sounds is varied by changing the
auditory-nerve-stimulation rate. In normal hearing physiology, as sound
pressure increases, hair cells 1100 are further deflected and action
potentials are fired at greater rates (linear relation). Graph 1110 shows
the amount of deflection of hair cells 1100. Graph 1120 shows the action
potential firing rates corresponding to the differing amounts of
hair-cell deflection shown in graph 1110. By varying the stimulation
rate, one can convey loudness. The greatest sustainable firing rate
(saturation) is about five-hundred (500) spikes per second (Kandel,
2000).

[0172] FIG. 12 is a graph 1200 of auditory nerve firing rate versus sound
level for acoustically stimulated hearing (i.e., nerve signals from
normal hearing in contrast to nerve signals from electrical or optical
stimulation of the nerve(s)). Increasing sound intensity causes the peak
of basilar membrane vibrations to get bigger, stimulating both inner and
outer hair cells (ihc/ohc) more. Increased stimulation of the hair cells
causes increased auditory nerve firing rates, as shown in 1200. The
response of the outer hair cells grows rapidly with increasing intensity
at low intensities, but more slowly at higher intensities (compressive).
A wide dynamic range is accomplished by this compressive response and by
the effect of low- and high-threshold neurons. Low-threshold neurons
saturate at low-to-mid sound levels. High-threshold neurons become active
at higher sound intensities, and saturate at higher sound intensities.

[0173] FIG. 13 is a graph 1300 of auditory nerve firing rate versus sound
level. Electric current stimulates the auditory nerve fibers in the
cochlea, producing action potentials that are conducted to the brain.
However, with direct auditory nerve stimulation without the inner hair
cells, the nerve fibers differ in threshold only slightly, so the dynamic
range of the combined response is much like the response of a single
nerve fiber. The result is a steepening of the combined firing-rate curve
for electrically stimulated nerves as compared to acoustically stimulated
nerves, shown in 1300.

[0174] FIG. 14 is a graph 1400 of perceived sound level versus auditory
nerve firing rate. If one considers perceived loudness as being driven by
auditory nerve firing rate (stimulation rate), the graph shows that
loudness (intensity) is a weak function of firing rate: even a large
change in firing rate generally results in a small change in perceived
loudness. Many papers seem to indicate that perceived loudness is a weak
function of stimulation rate in electrical and optical stimulation,
including McKay (1998), Vandali (2000), and Littlefield (2010).

[0175] FIG. 15 is a set of graphs 1500 (McKay, 1998) of test subject
loudness perception at differing electrical-stimulation pulse rates. As
described in McKay (1998), cochlear-implant listeners were asked to
balance loudness between a test signal at a number of stimulation rates
versus a reference signal at a 50-pulses-per-second (pps) stimulus rate.
As the perceived loudness of the test signal increased at increasing
stimulation rates, the test subjects reduced the strength of the test
signal to keep its perceived loudness equal to that of the reference
signal. It is clear that, at comfortably loud levels, subjects reduced
the strength of the test signal by relatively small amounts (less than 2
dB) over a large range (1000 pps) of stimulation rates. These test
results show that increasing auditory-nerve-stimulation rates
significantly, results in only small increases in perceived loudness of
sounds.

[0176] FIG. 16 is a set of graphs 1600 (McKay, 1998) of test subject
average auditory nerve spike probability versus stimulation rate. As
described in McKay (1998), the small increases in perceived loudness with
increasing stimulation rate are most likely a result of auditory nerve
action potential spike probability dropping with increased stimulation
rate, which has been observed in optical stimulation (Littlefield, 2010).
The data in 1600 show a drop after 100 pps.

[0177] FIG. 17A and FIG. 17B are graphs (Vandali, 2000) of signal current
level for various auditory-nerve-stimulation rates. FIG. 17A presents
data from Test Subject 1; FIG. 17B presents data from Test Subject 3. In
an experiment described in Vandali (2000), cochlear-implant listeners set
current levels for all electrodes in their cochlear implant for three
different stimulation rates. In these graphs, current level units are
clinical units (that use a 2% increase per step). The tests were
conducted at various sound levels, including threshold (t-level) and
maximum comfortable loudness (c-level). It is clear that stimulation rate
did not affect loudness settings significantly. There is only an
approximately 1-2 dB variation in perceived signal loudness at the
different stimulation rates (which varies with subject).

[0178] FIG. 18A is a graph 1801 of action potential rates versus frequency
for acoustically stimulated nerves, FIG. 18B is a set of graphs 1802 of
the distribution of numbers of neurons versus frequency, FIG. 18C is a
graph 1803 of nerve action potential response rate versus stimulation
rate, and FIG. 18D is a graph 1804 of nerve-firing efficiency versus
optical-stimulation rate, all of which show experimental data presented
in Littlefield (2010). In experiments described in Littlefield (2010),
single auditory nerves of normal-hearing gerbils were first acoustically
stimulated, and recordings were made from 403 neurons. The center
frequencies of the stimulation sounds were between 118 Hz and 22 kHz.
1801 is a graph of the maximum action potential rates versus stimulation
frequency for the observed neurons. The average maximum action potential
rate was 158±82 (158 plus-or-minus 82) action potentials per second.
Graph A 1802 in FIG. 18B shows the number of neurons (i.e., how many)
that responded to each frequency.

[0179] Two diode lasers were then used for stimulation of the auditory
nerves. They operated between 1.844 μm and 1.873 μm, with pulse
durations of 35 μs to 1,000 μs, and at repetition rates up to 1,000
pulses per second (pps). The laser outputs were coupled to a
200-μm-diameter optical fiber placed against a round window membrane
and oriented toward the spiral ganglion and at a distance 0.5 mm from the
spiral ganglion in the basil turn. Neural activity was recorded for
different laser radiant exposures, pulse durations, and
stimulus-repetition rates. The recordings were taken from 154 single
neural fibers, 67 of which showed stimulation responses. 1802 graph B
shows the number of neurons that responded to the optical stimulation
plotted against their characteristic frequencies: 67 neurons having
characteristic frequencies with a range of 450 Hz to 20 kHz responded.
1802 graph C shows the number of neurons that did not respond to the
optical stimulation plotted against their characteristic frequencies: 87
neurons having characteristic frequencies with a range of 148 Hz to 10
kHz did not respond to the optical stimulation. Graph 1803 in FIG. 18C
shows the action potential firing rate versus the
auditory-neuron-stimulation rate. The number of evoked action potentials
is fairly flat as stimulation rate is increased. It can be seen that the
laser-evoked response rates were lower than with acoustic stimulation.
The average maximum action potential rate was 97 plus-or-minus 53 action
potentials per second. Graph 1804 in FIG. 18D, which plots neuron firing
efficiency versus stimulation rate, shows that firing efficiency drops
after 100 pulses per second (pps).

[0180] FIG. 19 is a graph 1900 (Fu et al., 1999) of phoneme recognition as
a function of stimulation rate in six Nucleus-22 cochlear implant
listeners. In some embodiments of the present invention, loudness is
encoded in stimulation rate. Data from Fu et al. (1999) indicates that
speech recognition requires repetition rates (auditory-nerve-stimulation
rates) at least about 150 pulses per second (pps). A damage threshold may
limit pulse-repetition rates to no more than about 300 pps (personal
communication from Claus-Peter Richter, Northwestern University, a
sometime collaborator of the inventors). For an optical-stimulation rate
in the range of 150-300 pps, a less than 2 dB dynamic range is expected.

[0181] FIG. 20 is a graph 2000 (Fu et al., 2000) of phoneme recognition as
a function of stimulus dynamic range of the electrical stimulus of a
cochlear implant. The data from Fu et al. (2000) in the graph are percent
correct phoneme recognition rates for 3 test subjects. Consonant and
vowel phonemes were tested separately, and tests were conducted at three
different signal-compression levels, p=0.1 (high), p=0.2 (medium) and
p=0.4 (low). In some embodiments, the design is based on the dynamic
range needed. The data from Fu et al. (2000), graph 2000, shows that the
stimulus dynamic range should be at least 5-10 dB. It has been shown that
the loudness of an electrical stimulus in microamps (μA) is analogous
to the loudness of an acoustic stimulus in dBs. Loizou (2006) showed that
a 5-dB dynamic range is sufficient for phoneme recognition, and that
electrical-stimulation cochlear implants provide at least a 5-dB-stimulus
dynamic range. Nelson (1996) showed that cochlear-implant listeners
perceive seven to forty-five (7-45) sound-intensity steps. Fu and Shannon
(Fu et al., 2000) showed that phonetic discrimination drops when the
dynamic range is less than 6-to-8 dB.

[0182] Using Both Optical and Electrical Stimulation in a Cochlear Implant

[0183] In some embodiments, the present invention provides an apparatus
and method in which one or more electrical-stimulation electrodes are
included at the apical end of the cochlear implant and used to evoke an
auditory sensation corresponding to low-audio-frequency content of the
sound in the environment, which is especially helpful in speech
recognition. As noted above, in conventional electrical-only cochlear
stimulation, one challenging problem is the spreading of the electrical
signal through the conductive fluid and tissue in the cochlea. Optical
stimulation does not suffer this problem and therefore has an advantage
in its ability to stimulate in a more specific manner, which leads to
higher spectral fidelity for the implantee. A challenge arises, however,
to stimulate the apical spiral ganglion cells which sense sound signals
at the lower frequency range (e.g., in some embodiments, less than about
250 Hz) because the size and shape of the implant does not readily reach
the apical end of the cochlea's openings (e.g., the larger of these
cochlear channels, the scala tympani, is typically used for the implant)
there is no spreading of the optical signal to illuminate and stimulate
the cells beyond the tip of the implant, deep in the cochlea.
Conventional electrical stimulators inserted to the same depth can access
these deeper regions because of the spread of electricity reaches nerves
deeper into the cochlea. In some embodiments of the cochlear implant
device of the present invention, twenty-two (22) audio-frequency channels
(or other suitable number of audio-frequency channels) are selected from
a set of at least that many total emitters of the device and used for
optical stimulation (these selected ones are sometimes called the active
optical-stimulation channels for sound sensations to be perceived by the
user and in some embodiments, are selected from a set of many more
available emitters in the device by empirical testing to determine the
ones that are most effective at each perceived frequency) along the
implantable region within the cochlea and one or more electrodes are used
at the deepest apical end of the implant to stimulate beyond the end of
the implant. This additional electrical-stimulation channel (or
electrical-stimulation channels each of which corresponds to one or more
audio-frequency channel) provides improved low-audio-frequency sensations
for the high spectral fidelity delivered by the optical stimulation from
6000 Hz down to the deepest implantable region (about 250 Hz), by
additionally providing stimulation deeper in the cochlea by one or more
electrodes at the end of the implant.

[0184] As used herein, an "audio-frequency channel" is the signal and/or
value representing audio power within a narrow band of audio frequencies,
and each "audio-frequency channel" refers to the entire path from the
audio processor to the optical-stimulation signal launched towards the
cochlea neural tissue for its frequency band. The audio processor
"dissects" the full spectrum of the input audio (e.g., using a
fast-Fourier transform (FFT), discrete cosine transform (DCT) or other
suitable algorithm or method) into a plurality of frequency bands (used
for the respective audio-frequency channels), each representing content
of audio power within a predetermined range of audio frequencies. An
"audio-frequency-channel bin" is a group of adjacent audio-frequency
channels that forms one of a plurality of subsets of the full set of
audio-frequency channels. In some embodiments, audio-frequency-channel
bins overlap with one another; for example, the first
audio-frequency-channel bin may include only audio-frequency channels
1-5, the second audio-frequency-channel bin may include only channels
4-8, the third audio-frequency-channel bin may include only channels
7-11, and so on (such that audio-frequency channels 4-5 are included in
both bin 1 and in bin 2 (such that bin 1 and bin 2 overlap by two
audio-frequency channels), while audio-frequency channels 7-8 are
included in both bin 2 and in bin 3 (such that bin 2 and bin 3 overlap by
two audio-frequency channels), but bin 1 and bin 3 do not overlap and
audio-frequency channel 6 is not included in either bin 1 or bin 3. In
this way, the method of the present invention can prevent simultaneous
activation of two or three of any three adjacent audio-frequency channels
during a single time frame or a time period having a predetermined number
of P (e.g., two or more) successive time frames. The variable "M"
represents the number of channels in the full set. The variable "N"
represents the maximum number of channels in the subset of channels that
are allowed to be activated at a given time. The value of N may vary over
time--e.g., N may have a larger value after a time period that had a
continued low level of audio, but may have a value that starts small and
gradually increases over time after a period of very low (quiet) audio in
order not to jolt or overstress the auditory portion of the patient's
brain, and may have a value that gradually decreases over time after a
period of very high (loud) audio that may have caused heat build-up in
one larger localized area (i.e., an area that is the destination of two
or more optical-stimulation channels) of the cochlea, or in the cochlea
as a whole. In addition, in some embodiments, as described herein, the
up-to-N channels that are selected for activation in a given time period
are selected so as to spread out the area over which stimulation light is
applied so as to avoid overheating small or localized areas in the
cochlea. The term "frame" or "time frame" is the smallest quantum of time
in which audio power is divided by the software and/or control
electronics of the present invention for the purposes of limiting heat
buildup, and in various embodiments each frame may be about 4
milliseconds (which results in 250 frames per second) to about 7
milliseconds (which results in about 141 samples per second). In some
embodiments, a running history of the most recent H values in each
channel and/or each bin is maintained, allowing the method of the present
invention to also limit the number of times any one channel or group of
channels may be activated within H successive time frames.

[0185] Optimizing the Pulse-Repetition Rate of an Optical Cochlear Implant

[0186] Limitations on the upper limit of optical-stimulation
pulse-repetition rate exist for optical-stimulation devices--limitations
that are based on deleterious heating effects in the cochlea. However,
speech recognition is also based on stimulation rate, and often benefits
from a higher stimulation pulse-repetition rate. In some embodiments of
the present invention, stimulation rate (i.e., pulse-repetition rate) is
optimized for the patient based on comfort levels, speech-recognition
scores, and temperature feedback from monitors in the cochlea. Thus, in
some embodiments, the methods of the present invention find practical
lower and upper limits to the rate of stimulation to increase the
speech-recognition scores while implementing safety limits to preventing
overheating. In some embodiments, stimulation is optimized for speech
recognition and is kept above 150 pulses per second (pps), based on
findings that speech recognition degrades below 150-pps
pulse-repetition-rate-per-channel (see, e.g., Qian-Jie Fu and Robert
Shannon, "Effect of Stimulation Rate on Phoneme Recognition by Nucleus-22
Cochlear Implant Listeners," J. Acoust. Soc. Am. 107, pp 589-597 (1999)).
In some embodiments, pulse-repetition-rate optimization is performed by
determining the number of stimulation channels that can be simultaneously
stimulated at a given pulse-repetition rate. In other embodiments,
pulse-repetition-rate optimization is performed by determining the
pulse-repetition rates to use per channel.

[0187] Loudness perceived by a patient is a weak function of stimulation
rate. Optical stimulation is limited to 150-to-300 pulses-per-second
(pps) range. In some embodiments, a stimulation rate of at least 150 pps
is required for speech recognition. In some embodiments, a stimulation
rate of no more than 300 pps is required to stay below the damage
threshold (e.g., the pulse-repetition rate that risks damage from heating
the tissue being optically stimulated or nearby tissue). This range of
pulse-repetition rates only allows less than 2 dB of loudness dynamic
range. Further, some experiments have shown firing efficiency drops
significantly with a stimulation pulse-repetition rate over 100 pps, and
the action potential rate plateaus after about 50-100 pps. Little or no
speech information can be conveyed through a stimulation rate below about
100 pps. This is not sufficient for improvement over current electrical
stimulation. Therefore, some embodiments encode loudness information in
the pulse width of the optical pulses used for stimulation.

[0188] Additionally, in some embodiments, stimulation rate is kept below a
rate which overheats the cochlea. In some embodiments, a temperature
monitor is placed inside the cochlea to monitor and feedback a
temperature for use in limiting the stimulation rate and/or other
parameters such as peak optical power, wavelength, and pulse width. In
other embodiments, the temperature of the cochlea is modeled.
Additionally, in some embodiments, the temperature monitor serves as a
feedback to a safety shut-off switch in the case of overheating. Further,
in some embodiments, the present invention provides a patient-activatable
electromagnetic emergency-off mechanism.

[0189] In some embodiments, the implanted device 110 includes a
"fail-safe" circuit 588 (see FIG. 5) that immediately (or after a short
predetermined amount of time) turns off all stimulation devices
(including lasers or other optical sources, as well as the
electrical-stimulation drivers) if and when communications are lost to
the externally worn device 111. In this way, if excess loudness or other
discomfort is perceived, the patient can simply remove the externally
worn device from their body and move it to a distance far enough away
from the implanted device that the wireless communications is
disconnected, in order to actuate the fail-safe circuit 588. In some
embodiments, the externally worn device 111 periodically transmits a
periodic "heart-beat" signal that, as long as it is detected (within each
successive time period of a predetermined duration) by the fail-safe
circuit 588, prevents the fail-safe circuit 588 from turning off all
stimulation devices, but once a predetermined amount of time passes in
which no "heart-beat" signal is detected, the fail-safe circuit 588 turns
off all stimulation devices.

[0190] In some embodiments, the present invention provides an apparatus
and method in which the stimulation rate is optimized for the patient
based on comfort levels, speech-recognition scores, and temperature
feedback from monitors in the cochlea. Stimulation can be optimized for
speech recognition and should be kept above 150 pulses per second (pps)
based on findings that speech recognition degrades below a 150-pps per
channel. Additionally, stimulation rate should be kept below a rate that
would overheat the cochlea. In some embodiments, one or more temperature
sensors or monitors are placed inside the cochlea to monitor and provide
feedback signals indicative of temperature for use in limiting the
stimulation rate and/or other parameters, such as peak optical power,
wavelength, and pulse width. Additionally, in some embodiments, the
temperature monitor generates a feedback signal to a safety shut-off
switch in the case of overheating. This problem is new, as optical
stimulation of the cochlea is new. In some embodiments, the apparatus
includes a patient emergency-off switch (e.g., electro-magnet in
externally worn device transmits a periodic signal through the skin to
keep the implant active). When patient removes externally worn device
from the head, the implant no longer receives the periodic signal and
turns off the stimulation signals).

[0191] Providing Enhanced Music Perception in an Optical Cochlear Implant

[0192] Patients having conventional electrical cochlear implants usually
do not enjoy the perception of music, as the electrical stimulation
cannot specifically excite the regions of the cochlea that tonotopically
represent the semitones of Western music. It would be nearly impossible
to place the electrodes exactly at the semitone locations. Further, even
if the electrodes were placed directly over the semitone regions, the
electrical signal would spread too much to specifically excite the
regions of interest. The use of optical sources to deliver light to the
cochlea for purposes of stimulation brings the advantage of increased
spectral, fidelity because the illumination can be more specifically
placed than electrical signals.

[0193] In some embodiments, a large plurality of light sources or
light-delivery devices are placed along the cochlea, but only a
relatively small fraction of them are used due to the limitation of power
delivery and a restriction on heat within the cochlea. The large number
of implemented emitters also allows selection of the best positions for
stimulation without a priori knowledge of the exact placement, since the
device can be tested, calibrated and optimized to pick the best emitters
that most exactly stimulate the desired locations, and periodically
repeat this process to reprogram and recalibrate the device. The ability
to choose the sources used further provides the ability to choose the
sources which illuminate the semitones found in Western music. This
ability to access the exact places in the cochlea where semitones are
psychophysically represented will improve musical perception in the
patient.

[0194] In one embodiment, a plurality of light sources are connected
through a series of fuses that can be "blown" to permanently disconnect
those devices that are not to be used, and thus select the desired
source(s) in the region of interest. In other embodiments, similar to a
programmable logic array, the logic is programmable and settable during
optimization of the device for the patient, and optionally reprogrammable
and re-settable during a later re-optimization. In some embodiments,
optical stimulation optimized, or at least improved, for music perception
is a user-selected mode of the cochlear implant. In some such
embodiments, optimization for music perception is one of a plurality of
user-selected modes. In some embodiments, music-perception optical
stimulation uses "N-of-M" signal coding, as described below. In other
embodiments, the sources selected to be used are re-programmably or
dynamically (i.e., non-permanently, reprogrammably, and/or in a manner
that changes over time) activated according to a stored table or other
mechanism within the implant and/or the externally worn device (e.g., a
device having a microphone, some audio-processing capability and a
wireless transmitter that transmits (to the implanted device) information
corresponding to the microphone-sensed audio).

[0195] In some embodiments, an audio processor analyzes the incoming audio
signal from the microphone or other input device and makes a
determination as to the content of the signal, that is, whether the audio
signal is primarily speech, or primarily music. In some embodiments, one
or more of the regions of the cochlea that are stimulated are
automatically changed to optimize either music perception or voice
perception, based on the device detecting primarily voice or primarily
music content in the received audio. In other embodiments, a
music-perception stimulation mode is selected, from one of a plurality of
listening modes, by the wearer of the implant manually activating an
electrical switch, a magnetic trigger, an accelerometer configured to
detect a tip of the head of the wearer, or other input device on the
external portion of the implant system. In some embodiments, the
frequency range stimulated in the cochlea can be changed depending on the
type of audio signal being received. In some embodiments, both the
bandwidth of the processed signal and the pitch range are dynamically
altered based on the listening mode (whether the mode is automatically
selected or user selected). In some embodiments, the incoming audio
signal is processed in a way that shifts the nerve regions being
stimulated (analogous to shifting the audio in frequency (higher or
lower)) to nerve regions that work better (or that are sensed to be more
enjoyable) for music perception.

[0196] In some embodiments, "semitone" is defined to mean the interval
between adjacent notes in the twelve-note equally tempered scale. The
frequency ratio between two adjacent semitones is 2 (1/12) (the 12th
root of two):

(Frequency of Semitone N)/(Frequency of Semitone N-1)=12th root of
two (Eqn. 1)

The twelve-note equally tempered scale is commonly used in Western music.
In other embodiments, the "semitone" for adjacent notes is based on other
scales or tunings which do not have equal ratios between semitones, or
which use a scale having equal ratios between notes but having other than
twelve notes. Examples of these other tunings include the historic
Pythagorean Tuning, and Just Intonation commonly used by A cappella
groups.

[0197] The objective in calibrating a cochlear implant to a specific
individual is to achieve pleasurable perception and/or improved
recognition of music. Causing the patient wearing the implant to perceive
the actual frequencies in a music source is not necessary. To enhance the
perception of music, the intervals between notes (musical pitches), being
played either simultaneously or successively, must be correctly perceived
by the patient. Intervals (the frequency difference) between notes can be
characterized as an integral number of semitones. There are multiple
definitions of "semitone" depending on, for example, type of music,
historic time period of music, type of musical instrument, and musical
culture (e.g., oriental versus western). Therefore, a cochlear implant in
a particular patient is calibrated so musical intervals sound pleasing to
that individual.

[0198] In some embodiments, calibration of an implant is performed as
follows. This particular method is analogous to a piano-tuning method
described by Fischer (1907/1975) in "Piano Tuning." An initial musical
pitch is chosen from which to perform the calibration. In some
embodiments, the initial pitch is a C4 frequency (commonly known as
middle C) as that pitch would be extracted from received audio signal of
music. In other embodiments, the initial pitch is C5 (the C one octave
middle C). In other embodiments, some other initial pitch is used. In the
following description of one embodiment, an initial pitch of C4 is used.
An optical-stimulation channel is assigned to C4 such that the
optical-stimulation channel triggers nerves in the cochlea near the
region of the cochlea that responds to the C4 pitch. See Omran (2011),
"Semitone Frequency Mapping to Improve Music Representation for Nucleus
Cochlear Implants" for a description of mapping particular frequencies to
locations along the basilar membrane. Next, an initial
optical-stimulation channel is assigned to the pitch C5 that stimulates
nerves in the cochlea near the region of the cochlea that responds to C5.
Again, from Omran (2011) an approximate location along the basilar
membrane can be determined. A C4-pitched tone and a C5-pitched tone are
played for the patient whose cochlear implant is being calibrated, and
those tones are received and processed into optical-stimulation output,
wherein in some embodiments, the two tones are played simultaneously (two
cochlear areas stimulated simultaneously), and then are alternated (the
two cochlear areas stimulated alternately). As the C4 and C5 tones
(simultaneous with one another and/alternating with one another) are
received and decoded, the optical-stimulation channel selected for C4 is
excited/operated, and the initial C5 site excited by the initial
optical-stimulation channel, and one or more alternate "C5" sites and
optical-stimulation channels near the one initially assigned to the pitch
C5 are excited/operated to "play" the C5 tone to the patient. Stimulation
of stimulation sites that are not quite "an octave apart" may be
perceived as discordant or unpleasant by the patient. The patient is
asked to choose which optical-stimulation channel provides the patient
with the best perception of two tones separated by an octave (sites that
cause the most pleasant or least discordant or unpleasant sensation), and
this optical-stimulation channel is assigned to the pitch C5. A
corresponding procedure is then repeated for the C3 pitch (stimulating
the C4 site and sites around an initial C3 site).

[0199] With octave pitches assigned to specific optical-stimulation
channels, the rest of the musical pitches are then calibrated. An initial
Optical-stimulation channel is assigned (see Omran, 2011) for the G3
pitch (G a musical fifth (5 semitones) above C3). An interval of a fifth
is used because most individuals, even those with no musical training can
identify a fifth: musically, it sounds pleasant (it is perceived as
pleasant). As in assigning optical-stimulation channels to the octave
pitches, C3 and G3 pitched tones are played (simultaneously and/or
alternately) for the patient. Optical-stimulation channels near the one
initially chosen for G3 are used to "play" the G3 tone, and patient
feedback used to assign the optical-stimulation channel that provides him
or her with the most pleasant sensation (hopefully, the best perception
of a musical fifth). The octave-determining process is repeated for the
G4 pitch (using the G3 site and a plurality of sites to locate one for G4
that is best perceived as an octave above G3). In some embodiments, as a
check, a G4 pitched tone is played with a C4 pitched tone (a musical
fifth interval), and the optical-stimulation channel assigned to G4
slightly adjusted so that both octave interval (above G3) and the fifth
interval (above C4) both sound most pleasant to the patient. The process
is repeated for other pitches in the musical scale, doing D4 (a fifth
above G3) next, then D3 (an octave below D4, and so on. In some
embodiments, the calibration is done using only intervals of octaves and
fifths, which are easy for most people to recognize. In some embodiments,
where the cochlear implant has an extended frequency range (more than 2
octaves), the above process is repeated to extend the perceived musical
range. In other embodiments, additional or alternative musical intervals
are used (such as musical thirds and/or sevenths). In some embodiments,
an additional process is used to identify a best set of immediately
adjacent semitones, wherein two adjacent semitones are discerned as
discordant when played simultaneously, but a scale of 8 or 12 successive
notes is perceived as "equally tempered" by the patient. In some
embodiments, the entire process or portions thereof is iteratively
repeated to fine tune the perception of an equally tempered scale and
harmonies formed from such a scale. In some embodiments, a succession of
chords of two or more simultaneous notes is played to further fine tune
the patient's perception of music.

[0200] In other embodiments, calibration of the cochlear implant is
performed by initially assigning optical-stimulation channels to all
pitches, for example, using the mathematics described in Omran (2011):
[0201] Equation 2 below describes the characteristic frequencies at
distance x mm from the cochlea's apex according to Greenwood's
empirically derived function which was verified against data that
correspond to a range of x from 1 to 26 mm,[12].

[0203] In some embodiments, after the initial assignment of
optical-stimulation channels, easily recognizable pieces of music are
played for the patient. A music-recognition score, based on feedback from
the patient, is used as a guide in fine tuning the assignment of
optical-stimulation channels to specific pitches.

[0204] In some embodiments, the present invention provides an apparatus
and method in which optical sources deliver light to small specific areas
of the cochlea for purposes of stimulation, which brings the advantage of
increased spectral fidelity (fine-grained audio frequency perceived by
the patient) because the stimulation illumination can be more
specifically placed than electrical-stimulation signals. Conventional
electrical-stimulation-only cochlear-implant patients often do not enjoy
the perception of music, as the electrical stimulation cannot
specifically excite the regions of the cochlea that tonotopically
represent the semitones of Western music. It would be nearly impossible
to place the electrodes exactly at the semitone locations in the cochlea.
But, even if the electrodes were placed directly over the semitone
regions, the electrical signal would spread too much to specifically
excite the regions of interest. In some embodiments of the present
invention, a plurality of light sources or light-delivery devices are
placed at finely-spaced locations along the cochlea, but only a fraction
of them are used within any short period of time due to the limitation of
power delivery to the optical emitters and a restriction on heat within
the cochlea due to the absorption of the optical-stimulation signals. The
ability to choose which optical sources are used at any given time frame
provides the ability to choose the sources that illuminate and thus
stimulate the particular small areas of the cochlea that generate nerve
signals perceived as the semitone frequencies found in Western music.
This ability to access the exact places in the cochlea where semitones
are psychophysically represented will improve musical perception by the
patient. In one embodiment, multiple sources are connected through a
series of fuses that can be "blown" to select the desired source in the
region of interest. Similar to a programmable logic array, the logic
could be programmable and settable during optimization of the device for
the patient. In other embodiments, the sources selected to be used are
re-programmably or dynamically (i.e., in a manner that changes over time)
activated according to a stored table or other mechanism within the
implant and/or the externally worn device (e.g., a device having a
microphone, some audio-processing capability and a wireless transmitter
that transmits (to the implanted device) information corresponding to the
microphone-sensed audio.

[0206] In electrical stimulation, the challenging problem is the spreading
of the electrical signal through the conductive fluid and tissue in the
cochlea. Optical stimulation does not suffer this problem and therefore
has an advantage in its ability to stimulate in a more specific manner,
which leads to higher spectral fidelity for the implantee. One challenge,
however, is heating of the tissue by the optical channels. Because the
physiological mechanism for stimulation using optical signals is thermal,
careful engineering is needed to allay thermal buildup in the cochlea. In
some embodiments, signal-coding strategies are used to reduce the number
of channels on at any given time and therefore reduce the average power
delivered and heat produced. In some embodiments, a commonly used coding
strategy is the "N-of-M" coding strategy, where the input frequency
spectrum is analyzed by the signal processor and spectral power is
dissected into M channels, then, by subsequently determining the N
channels with the highest power, those channels are stimulated by the
corresponding electrodes in the implant. In some embodiments, this is
done frame by frame, where the frame rate is the refresh rate of the data
processor (in some electrical cochlear implants, this is done for the
reason that electrical implantees cannot utilize more than 8 channels due
to electrical spread in the cochlea).

[0207] In some embodiments, an N-of-M coding strategy is used, while
placing a quota on the number of channels selected to illuminate in each
frame. Speech tends to fill the audio frequency spectrum between 50-6000
Hz and conventional electrical-stimulation cochlear implant speech
processors tend to cover the range 240-6000 Hz, depending on insertion
depth. In some embodiments of the present optical-simulation
cochlear-implant invention, an audio range of 50-6000 Hz or other
suitable range is used, wherein this total audio range is broken into 22
(or other suitable number of) audio-frequency channels and 11 (or other
suitable subset number of) these audio-frequency channels are illuminated
at each time-frame cycle (sometimes simply called "frame" herein). In
other embodiments, rather than simply illuminate the 11 frequency-based
channels of the detected audio spectrum having the highest power during a
given time-frame cycle, there is a quota to illuminate at least X
channels from each bin of channels (wherein, in some embodiments, for
some bins, X is zero or more, while for other bins, X may be one, two, or
more channels) and no more than Y channels from each bin. This limits the
number of illuminated channels-per-length of cochlea and therefore
prevents localized heating of the cochlea and reduces power consumption
of the device. In some embodiments, rather than using non-overlapping
bins (wherein the lowest-frequency channels of one bin could be
contiguous with the highest-frequency channels of an adjacent bin),
overlapping bins are used, such that the Y limit on channels (i.e., how
many channels in one bin that are allowed to be active in a given
predetermined period of time) applies to adjacent areas that might have
been in different bins if non-overlapping bins were to be used.

[0208] In some embodiments, the present invention provides an apparatus
and method in which a subset of N frequency-based stimulation channels
are selectively activated from a set of M measured frequency-based audio
values (N-of-M coding) for each given time frame. One coding strategy
used in conventional electrical-stimulation cochlear implants is an
N-of-M coding strategy, where the input frequency spectrum is analyzed by
the signal processor and spectral power is dissected into M
frequency-based channels, then, by subsequently determining the N
channels with the highest power, those channels are activated to
stimulate the corresponding electrodes in the implant. This is done frame
by frame, where the frame rate is the refresh rate of the data processor.
This is done for the reason that some conventional electrical implantees
cannot utilize more than eight (8) channels due to electrical spread
through the conductive fluid and tissue in the cochlea. Optical
stimulation does not suffer this "spreading" problem and therefore has an
advantage in its ability to stimulate in a more specific and fine-grained
manner, which leads to higher spectral fidelity for the implantee. One
challenge, however, is heating of the tissue by the optical channels
(particularly when activating many channels that are close in space
and/or that are activated close in time). Because the physiological
mechanism for stimulation using optical signals is thermal (i.e., heat is
needed to trigger the desired CNAPs, careful engineering is needed to
allay thermal buildup in the cochlea. In some embodiments of the present
invention, signal coding strategies are used to reduce the number of
channels active within a predetermined amount of time and within a given
volume of tissue, therefore controlling (limiting a maximum amount of)
the average power delivered and heat produced. In some embodiments, an
N-of-M coding strategy is used for the optical stimulation of the cochlea
(or other neural tissue) that is different than those used for electrical
stimulation. In some embodiments, the optical N-of-M coding place a quota
on the number of and spacing of frequency channels selected to illuminate
tissue during each time frame. Speech tends to fill the frequency
spectrum between 50-6000 Hz and cochlear-implant speech processors tend
to cover the range 240-6000 Hz, depending on insertion depth. In some
embodiments, the present invention breaks this range into 22 (or other
suitable total number) frequency-based channels and limits the optical
stimulation generated to illuminate a maximum of 11 (or other suitable
subset number) at each time-frame cycle. In some embodiments, the total
number of frequency-based channels is divided into a plurality of
adjacent-frequency-based "bins," wherein each bin corresponds to one or
more optical emitters within the cochlea that are close to one another in
space (and thus each bin corresponds to a subset of adjacent frequencies
within the spectrum of audio frequencies used by the audio processor. In
some embodiments, rather than simply activating the 11 highest-power
channels, some embodiments use a quota to illuminate at least X channels
from each bin of channels for a plurality of bins (e.g., in some
embodiments, depending on the frequency content and loudness of the
sounds received by the microphone the number of bins having this minimum
number of channels activated may vary) and no more than Y channels from
any one bin. This limits the number of activated channels (adjacent
illuminated areas) per unit length (or volume, in some embodiments) of
cochlea and therefore prevents localized overheating of the cochlea and
reduces power consumption of the device.

[0209] Optimization of Individual Performance of an Optical Cochlear
Implant

[0210] When a patient is implanted with a cochlear implant, the implant
remains off for a period of time while the patient's body adapts to the
implant. The patient then visits an audiologist to initiate use of the
device and set parameters for best operation in the individual.

[0211] In some embodiments, a plurality of parameters is specified by the
computer program used to implement the optimization of the present
invention, or specified to the program by the audiologist (or patient)
utilizing the program, as potential mechanisms for optimizing implant
performance for the individual patient. In some embodiments, the
following parameters are used to encode information on the optical
signal: pulse width, peak power, stimulation rate, wavelength,
polarization, wavelength profile; beam profile, beam angle.

[0212] In some embodiments, the following parameters are used to optimize
the implant performance during tuning of the device after implantation:
pulse width, amplitude, frequency, wavelength, polarization, wavelength
profile, beam profile, beam angle, coding strategy (e.g., N-of-M),
signal-processing filter bandwidths, signal-processing filter shapes,
signal-processing filter center frequencies, and operational/functioning
channels. Individual patients may find a range of comfort levels and
settings that provide best performance of the device for each one of a
plurality of different listening environments (driving a car, voice
conversations, music listening and the like). In some embodiments, the
audiologist adjusts the above parameters to provide the patient with best
performance. In some embodiments, best performance is judged by speech
recognition, loudness comfort levels, physical comfort, and/or device
battery life between rechargings of the battery.

[0213] In some embodiments, the present invention provides an apparatus
and method in which an audiologist's console computer when a
cochlea-stimulation device is implanted into a patient, the implant is
programmed to remain off for a period of time while the patient's body
adapts to the implant. The patient then visits an audiologist to initiate
use of the device and set parameters for best operation in the
individual. The audiologist's console computer is programmed to provide
the capability to customize operation of the implanted device while
preventing programming of combinations of device operations that could be
harmful to the patient or the device. The present invention provides many
parameters that are individually settable by the customization program as
potential mechanisms for optimizing implant performance for the
individual patient. In some embodiments, one or more of the following
parameters can be used to encode information on the optical signal: pulse
width, peak power, intensity profile over time, stimulation rate,
wavelength, polarization, wavelength profile (as a function of spatial
location, tissue type, recent-past history of stimulation in a given
area, and the like), beam spatial intensity profile, beam angle and the
like. In some embodiments, the following parameters can be used to
optimize the implant's performance during tuning of the device after
implantation: pulse width, amplitude, frequency, wavelength,
polarization, wavelength profile, beam profile, beam angle, coding
strategy (i.e., N-of-M), signal-processing filter bandwidths,
signal-processing filter shapes, audio-signal-processing-filter center
frequencies, selection of operational and/or best-functioning channels,
and the like. Individual patients may empirically determine a range of
comfort levels and settings that provide best performance of the device.
The audiologist may adjust the above parameters to provide the patient
with best performance. In some embodiments, the patient is provided with
a program that they may take home and run on any suitable personal
computer, wherein the program is configured to have the computer audibly
output a set of calibration tones, tunes, speech or other sounds and to
elicit and receive input indications from the patient, and to analyze
that input to calculate parameters to be used by the implanted device
(and/or the externally-worn device having one or more microphones, power,
and sound-processing capability). In some embodiments, "best" performance
may be judged by speech recognition, loudness comfort levels, physical
comfort, and device battery life.

[0214] In some embodiments, the pulse-repetition rate is customized and
optimized for the individual during system tuning after implantation. In
some embodiments, the peak power of the light signal is customized and
optimized for the individual during system tuning after implantation.

[0215] In some embodiments, a set of optimal values for pulse-repetition
rate, peak power and range of pulse width is determined for each of a
number of specific listening environments and sound sources of interest.
For example, one set of parameters is optimized for listening to a male
voice in a quiet environment. Another set of parameters is optimized for
listening to a male voice in a noisy environment (e.g., a crowded room).
A third set of parameters is optimized for listening to a female voice in
a noisy environment (e.g., a crowded room). Listening environments
include, but are not limited to, quiet, many other voices (e.g., a room
crowded with people), road noise (e.g., riding in a car or other
vehicle), and street noise (e.g., walking along a busy street). Exemplary
sound-source environments include, but are not limited to, male or female
voice conversations, music, and sounds of nature (e.g., bird calls while
bird watching).

[0216] In some embodiments, the user of the cochlear implant selects the
set of operating parameters (pulse-repetition rate, peak power and pulse
width range) to use at any point in time. The selection is made using a
device external to the cochlear implant. In some embodiments, the
external device is included with an external sound-receiving and
signal-processing element that drives the cochlear implant. In other
embodiments, a separate device is used that is coupled to the
cochlear-implant controller magnetically, via radio frequency signals,
via light signals, or via other means. In some embodiments, the
controller for the cochlear implant makes an operating-parameter
selection based on the controller's analysis of the listening
environment. In some embodiments, a collection of sets of operating
parameters is provided by the manufacturer of the cochlear implant. In
some embodiments, a collection of sets of operating parameters is
provided by the audiologist or physician implanting the cochlear implant.
In some embodiments, a collection of sets of operating parameters is
determined by empirically testing the responses of the wearer of the
cochlear implant. In some embodiments, some combination of sources is
used to determine the collection of available sets of operating
parameters.

[0218] Experiments (see Izzo et al.: "Optical Parameter Variability in
Laser Nerve Stimulation: a study of pulse duration, repetition rate, and
wavelength," 2006; later published in IEEE Trans Biomed Eng. 2007 June;
54(6 Pt 1):1108-14) have shown that neural compound action potentials
(CAPs) can be evoked by pulsed optical stimulation and the magnitude of
the action potential is a function of the peak power of the incident
pulses for pulses shorter than approximately 100 microseconds (μs). As
pulses are shortened and peak power is held constant, the CAP reduces. In
some embodiments, this effect is utilized to encode loudness information,
as the CAP level determines perceived loudness.

[0219] In some embodiments, pulse-repetition rate and peak power are held
constant, while pulse width is modulated to evoke a sufficient range of
CAPs, encoding sound information for the listener. An advantage of this
method of encoding is the CAP can be very sensitive to pulse width in
this regime, and therefore pulse width is a useful parameter to achieve a
large range of stimulation for a small change in pulse width. In one
embodiment, the pulse width is customized and optimized for the
individual during system tuning after implantation.

[0220] In some embodiments, an optimal range of pulse widths is determined
(in some such embodiments, the intensity may or may not vary). In some
embodiments, the temporal shape of pulses is optimized. In some
embodiments, different emitters are used for different portions of pulse.

[0221] In some embodiments, the present invention provides an apparatus
and method in which pulse-width modulation is applied to the
optical-stimulation pulses to the cochlea nerves to obtain an increased
dynamic range (a variation in the loudness perceived by the patient).
Experiments (Izzo, 2006) have shown that neural compound nerve-action
potentials (CNAPs, also called CAPs) can be evoked by pulsed optical
stimulation and the magnitude of the action potential is a function of
the peak power of the incident pulses for pulses shorter than about 100
microseconds (μs). As pulses are shortened and peak power is held
constant, the CAP reduces. This effect can be utilized to encode loudness
information, since the CAP level determines perceived loudness. In some
embodiments of the present invention, pulse-repetition rate and peak
pulse power are held constant, while pulse width is modulated to evoke a
sufficient dynamic range of CAPs (i.e., different CAP strengths), thus
encoding sound-loudness information for the listener. An advantage of
this method of encoding is the CAP can be very sensitive to pulse width
in this regime, and therefore optical-pulse width is a useful parameter
to vary, and this achieves a large range of stimulation for a small
change in pulse width. In some embodiment, the pulse width is adjusted to
be optimized for the individual during successive system-tuning sessions
after implantation.

[0222] Using a Broad Wavelength Profile To Homogenize The Absorption
Profile In Optical Stimulation Of Nerves

[0223] In some embodiments, the present invention provides an apparatus
and method in which the power-versus-wavelength spectrum of the optical
stimulation light is customized to achieve a desired spatial-absorption
pattern. In electrical stimulation, one challenging problem is the
undesired spreading of the electrical signal through the conductive fluid
and tissue in the cochlea. The optical stimulation of the present
invention does not suffer this problem and therefore has an advantage in
its ability to stimulate in a more specific manner (i.e., to trigger
CNAPs for narrower audio frequency ranges (more specific frequencies),
for an increased number of different audio frequency ranges (the narrower
and more numerous audio frequency ranges result from the optical
stimulation that does not spread to adjacent tissues as much as
electrical stimulation does), and for a greater range of different
loudness levels (increased dynamic range), which leads to higher spectral
fidelity for the implantee. A challenge that the present invention solves
is to deliver a stimulation signal that triggers CNAPs that are perceived
as quite different loudnesses, i.e., as sounds with a substantial dynamic
range. The physical extent (the volume) of the stimulated region is
limited by the absorption profile of the spiral ganglion cells (or other
suitable tissue cells) that are being stimulated, and by the fluence of
the optical spot at the tissue interface. The absorption coefficient is
wavelength dependent and therefore the spatial absorption profile is
wavelength dependent. When a spot of light illuminates the modiolus and
reaches the spiral-ganglion-cell interface, the cells absorb light
according to their optical absorption coefficient. Because the light
experiences exponential decay as it travels through the volume of cells,
the absorption profile in the illuminated volume is exponential in
nature, and more light is absorbed near the surface and less is absorbed
deeper in the tissue (see FIG. 4, FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, and
FIG. 4E). FIG. 4 is a color-coded plot of a temperature profile of tissue
due to absorption of single-wavelength source of infrared light. When a
single wavelength is used to stimulate (as in FIG. 4, FIG. 4A, FIG. 4B,
and FIG. 4C), there exists a limited range of fluence that can be
utilized for stimulation. There is a minimum fluence to reach the hearing
threshold and, as the fluence is increased, deeper cells are recruited
for stimulation but a limitation is reached when the interface tissue,
where the bulk of the absorption is taking place, becomes too hot. The
exponential profile of absorption is unwanted if a large dynamic range is
desired, which is the case in some embodiments of the present invention.
In some embodiments, a broad linewidth source (e.g., see FIG. 3A, FIG.
3C, and FIG. 3E) is used with an optimized wavelength profile that
homogenizes the absorption profile in the tissue. In one embodiment, the
profile may dynamically change as the power is increased, optimizing the
absorption profile. One advantage of this solution is that the dynamic
range is extended due to the even spread of absorption in the illuminated
volume. As shown in FIG. 3A, FIG. 3C, FIG. 3E, FIG. 4D, and FIG. 4E, in
some embodiments, a broad wavelength source is used with a
power/wavelength profile that is designed and crafted to homogenize the
absorption in the tissue. As shown in FIG. 4F, FIG. 4G and FIG. 4H, in
some embodiments, the wavelength source has a power/wavelength profile
that is designed and crafted to change over time such that the absorption
in the tissue is customized to obtain the desired triggering of NAPs.

[0224] In some embodiments, the first predetermined amount of energy is
the same as the second predetermined amount of energy, but the power of
one is increased and the duration is decreased by a compensating value
such that even though the amounts of energy are the same, the peak powers
are different. In some embodiments, this is the result of using different
pulse shapes, wherein pulse shape is defined as the amount of power as a
function of time.

[0225] In some embodiments, the first pulsed optical-stimulation signal
has a first pulse at the first wavelength that starts at a first starting
point in time and a second pulse at the second wavelength that starts at
a second starting point in time, and wherein the first starting point of
the signal at the first wavelength is different than the second starting
point of the signal at the second wavelength and both the first and
second pulses contribute to triggering the same NAP or CNAP (i.e., a
single NAP or a single CNAP). In other embodiments, the first pulsed
optical-stimulation signal has a first pulse at the first wavelength that
ends at a first ending point in time and a second pulse at the second
wavelength that ends at a second ending point in time, and wherein the
first ending point of the signal at the first wavelength is different
than the second ending point of the signal at the second wavelength, and
both the first and second pulses contribute to triggering the same NAP or
CNAP. In either case, the pulses are not simultaneous, but they are
partially overlapped, or at least nearby in time so as to be synergistic
in triggering one NAP or CNAP.

[0226] Further Discussion of Encoding Information in an Optical Cochlear
Implant with Minimal Heat Effects in the Cochlea

[0227] In some embodiments, the present invention includes a method for
optically stimulating neurons of a cochlea of a person. In some
embodiments, the method includes obtaining an audio signal having an
audio spectrum, and, for each of a plurality of successive time frames
including a first, second, third and fourth time frame, generating a
plurality of "M" audio channels of the audio spectrum, each of the
plurality of "M" channels for one of the plurality of time frames having
a sub-portion of frequencies of the audio spectrum for a period of time
corresponding to that one of the plurality of frames. For each of the
plurality of time frames, the method further includes selecting a subset
of "N" audio channels selected from the "M" channels by an "N of M"
coding strategy, for each one of the subset of "N" channels, generating a
corresponding pulsed light signal having one or more successive pulses
that, when applied to a neuron of a person, will each stimulate a nerve
action potential (NAP) in the neuron, and delivering the generated
corresponding pulsed light signals to a corresponding one of a plurality
of frequency-specific locations in the cochlea of the person to optically
stimulate one or more neurons in the cochlea in order to trigger NAPs in
the one or more neurons of the cochlea.

[0228] In some embodiments, the "M" channels are organized into a
plurality of bins, each of the plurality of bins having a plurality of
channels, and where, for each bin, the selected subset of "N" channels
includes a maximum of fewer than all channels within that one bin. In
other embodiments, selecting the subset of "N" channels includes
selecting a minimum of at least "X" channels from each of the plurality
of bins, and selecting a maximum of no more than "Y" channels from each
of the plurality of bins. In some embodiments, "X" is greater than one
and "Y" is greater than "X". In some embodiments, adjacent ones of the
channels of the plurality of channels in each bin are directed towards
neurons that, when triggered, are perceived by the person to be adjacent
to each other in frequency.

[0229] In some embodiments, each of the plurality of "M" channels is only
in a single bin. In other embodiments, a subset of the plurality of
channels in each bin is also in an adjacent bin, where a first frequency
range covered by the adjacent channels in a first bin partially overlaps
with a second frequency range covered by the adjacent channels in a
second bin.

[0230] In some embodiments of the present invention, selecting the subset
of "N" channels includes selecting an individual one of the "M" channels
at no more than two successive time frames during the plurality of
successive time frames. In some embodiments, the selected subset of "N"
channels during the first time frame includes the eleven channels
corresponding to the eleven portions of the audio spectrum having the
strongest signal selected from the "M" channels during the first time
frame, where the first time frame is in a range of approximately 4
milliseconds to 7.5 milliseconds.

[0231] In some embodiments, the method further includes providing a
plurality of vertical-cavity-surface-emitting lasers (VCSELs), where the
plurality of VCSELs performs the generating of the corresponding pulsed
light signal. In some embodiments, more VCSELs are provided than are
necessary during any one time frame for triggering NAPs in the one, or
more neurons of the cochlea.

[0232] Some embodiments of the present invention include an apparatus for
optically stimulating neurons of a cochlea of a person, wherein the
apparatus includes a means for obtaining an audio signal having an audio
spectrum, a means for generating a plurality of "M" audio channels of the
audio spectrum for each of a plurality of successive time frames
including a first, second, third and fourth time frame, each of the
plurality of "M" channels for one of the plurality of time frames having
a sub-portion of frequencies of the audio spectrum for a period of time
corresponding to that one of the plurality of frames, a means for
selecting for each of the plurality of time frames a subset of "N" audio
channels selected from the "M" channels by an "N of M" coding strategy, a
means for generating for each of the plurality of time frames a
corresponding pulsed light signal having one or more successive pulses
for each one of the subset of "N" channels that, when applied to a neuron
of a person, will each stimulate a nerve action potential (NAP) in the
neuron, and a means for delivering for each of the plurality of time
frames the generated corresponding pulsed light signals to a
corresponding one of a plurality of frequency-specific locations in the
cochlea of the person to optically stimulate one or more neurons in the
cochlea in order to trigger NAPs in the one or more neurons of the
cochlea.

[0233] In some embodiments, the channels of the plurality of "M" channels
are organized into a plurality of bins, each of the plurality of bins
having a plurality of channels, and where, for each bin, the selected
subset of "N" channels includes a maximum of fewer than all channels
within that one bin. In some embodiments, the means for selecting the
subset of "N" channels includes means for selecting a minimum of at least
"X" channels from each of the plurality of bins, and means for selecting
a maximum of no more than "Y" channels from each of the plurality of
bins.

[0234] In some embodiments, adjacent ones of the channels of the plurality
of channels in each bin are directed towards neurons that, when
triggered, are perceived by the person to be adjacent to each other in
frequency. In some embodiments, each of the plurality of "M" channels is
in at most a single bin (i.e., each of the plurality of "M" channels is
in one and only one bin). In other embodiments, a subset of the plurality
of channels in each bin is also in an adjacent bin, where a first
frequency range covered by the adjacent channels in a first bin partially
overlaps with a second frequency range covered by the adjacent channels
in a second bin.

[0235] In some embodiments of the present invention, the means for
selecting the subset of "N" channels includes means for selecting an
individual one of the "M" channels at no more than two successive time
frames during the plurality of successive time frames. In other
embodiments, the selected subset of "N" channels during the first time
frame includes the eleven channels corresponding to the eleven portions
of the audio spectrum having the strongest signal selected from the "M"
channels during the first time frame. In some embodiments, the first time
frame is in a range of approximately 4 milliseconds to 7.5 milliseconds.

[0236] In some embodiments, the means for generating the corresponding
pulsed light signals includes a plurality of
vertical-cavity-surface-emitting lasers (VCSELs). In some embodiments,
the means for generating further includes means for activating, at
different times, more VCSELs than are necessary during any one time frame
for triggering NAPs in the one or more neurons of the cochlea. In some
embodiments, at least four times more VCSELs are implemented than will be
activated during normal operation of the device toward a single
frequency-response region of the cochlea within any two successive time
frames.

[0237] Some embodiments of the present invention include an apparatus for
optically stimulating neurons of a cochlea of a person. In some
embodiments, the apparatus includes an audio sensor configured to obtain
an audio signal having an audio spectrum, an audio processor configured
to generate a plurality of "M" audio channels of the audio spectrum for
each of a plurality of successive time frames including a first, second,
third and fourth time frame, each of the plurality of "M" channels for
one of the plurality of time frames having a sub-portion of frequencies
of the audio spectrum for a period of time corresponding to that one of
the plurality of frames, a channel mapper configured to select for each
of the plurality of time frames a subset of "N" audio channels selected
from the "M" channels by an "N of M" coding strategy, an optical
generator configured to output, for each of the plurality of time frames,
a corresponding pulsed light signal having one or more successive pulses
for each one of the subset of "N" channels that, when applied to a neuron
of a person, will each stimulate a nerve action potential (NAP) in the
neuron, and an optical guide configured to deliver, for each of the
plurality of time frames, the generated corresponding pulsed light
signals to a corresponding one of a plurality of frequency-specific
locations in the cochlea of the person to optically stimulate one or more
neurons in the cochlea in order to trigger NAPs in the one or more
neurons of the cochlea.

[0238] In some embodiments, the "M" channels are organized into a
plurality of bins, each of the plurality of bins having a plurality of
channels. For each bin, the selected subset of "N" channels includes a
maximum of fewer than all channels within that one bin. In some
embodiments, the channel mapper is further configured to select the
subset of "N" channels such that the subset of "N" channels includes a
minimum of at least "X" channels from each of the plurality of bins, and
a maximum of no more than "Y" channels from each of the plurality of
bins.

[0239] In some embodiments, adjacent ones of the channels of the plurality
of channels in each bin are directed towards neurons that, when
triggered, are perceived by the person to be adjacent to each other in
frequency. In some embodiments, each of the plurality of "M" channels is
in a single bin. In other embodiments, a subset of the plurality of
channels in each bin is also in an adjacent bin, such that a first
frequency range covered by the adjacent channels in a first bin partially
overlap with a second frequency range covered by the adjacent channels in
a second bin.

[0240] In some embodiments, the channel mapper is further configured to
select the subset of "N" channels, such that the subset of "N" channels
includes an individual one of the "M" channels at no more than two
successive time frames during the plurality of successive time frames. In
other embodiments, the selected subset of "N" channels during the first
time frame includes the eleven channels corresponding to the eleven
portions of the audio spectrum having the strongest signal selected from
the "M" channels during the first time frame, and wherein the first time
frame is in a range of approximately 4 milliseconds to 7.5 milliseconds.
In some embodiments, the optical generator includes a plurality of
vertical-cavity-surface-emitting lasers (VCSELs). In some embodiments,
the optical generator further includes more VCSELs than are necessary
during any one time frame for triggering NAPs in the one or more neurons
of the cochlea.

[0241] Some embodiments of the present invention include a non-transitory
computer readable medium having instructions stored thereon for causing a
suitably programmed information processor to perform a method for
optically stimulating neurons of a cochlea of a person. In some
embodiments, the method includes obtaining an audio signal having an
audio spectrum. For each of a plurality of successive time frames
including a first, second, third and fourth time frame, the method
further includes generating a plurality of "M" audio channels of the
audio spectrum, where each of the plurality of "M" channels for one of
the plurality of time frames has a sub-portion of frequencies of the
audio spectrum for a period of time corresponding to that one of the
plurality of frames. For each of the plurality of time frames, the method
further includes selecting a subset of "N" audio channels selected from
the "M" channels by an "N of M" coding strategy, for each one of the
subset of "N" channels, generating a corresponding pulsed light signal
having one or more successive pulses that, when applied to a neuron of a
person, will each stimulate a nerve action potential (NAP) in the neuron,
and delivering the generated corresponding pulsed light signals to a
corresponding one of a plurality of frequency-specific locations in the
cochlea of the person to optically stimulate one or more neurons in the
cochlea in order to trigger NAPs in the one or more neurons of the
cochlea.

[0242] In some embodiments, the non-transitory computer readable medium
includes instructions such that the plurality of "M" channels is
organized into a plurality of bins, each of the plurality of bins having
a plurality of channels, where, for each bin, the selected subset of "N"
channels includes a maximum of fewer than all channels within that one
bin. In other embodiments, selecting the subset of "N" channels includes
selecting a minimum of at least "X" channels from each of the plurality
of bins, and selecting a maximum of no more than "Y" channels from each
of the plurality of bins.

[0243] In some embodiments, the non-transitory computer readable medium
includes instructions such that the audio channels in each bin are
adjacent to each other in frequency. In some embodiments, each of the
plurality of "M" channels is in a single bin. In other embodiments, a
subset of the plurality of channels in each bin is also in an adjacent
bin, and a first frequency range covered by the adjacent channels in a
first bin partially overlaps with a second frequency range covered by the
adjacent channels in a second bin.

[0244] In some embodiments, selecting the subset of "N" channels includes
selecting an individual one of the "M" channels at no more than two
successive time frames during the plurality of successive time frames. In
some embodiments, the selected subset of "N" channels during the first
time frame includes the eleven channels corresponding to the eleven
portions of the audio spectrum having the strongest signal selected from
the "M" channels during the first time frame. In some embodiments, the
first time frame is in a range of approximately 4 milliseconds to 7.5
milliseconds.

[0245] In some embodiments of the present invention, the method further
includes providing a plurality of vertical-cavity-surface-emitting lasers
(VCSELs), where the plurality of VCSELs performs the generating of the
corresponding pulsed light signal. In some embodiments, the providing
includes providing more VCSELs than are necessary during any one time
frame for triggering NAPs in the one or more neurons of the cochlea.

[0246] It is specifically contemplated that the present invention includes
embodiments having combinations and subcombinations of the various
embodiments and features that are individually described herein and in
patents and applications incorporated herein by reference (i.e., rather
than listing every combinatorial of the elements, this specification
includes descriptions of representative embodiments and contemplates
embodiments that include some of the features from one embodiment
combined with some of the features of another embodiment). Further, some
embodiments include fewer than all the components described as part of
any one of the embodiments described herein.

[0247] It is to be understood that the above description is intended to be
illustrative, and not restrictive. Although numerous characteristics and
advantages of various embodiments as described herein have been set forth
in the foregoing description, together with details of the structure and
function of various embodiments, many other embodiments and changes to
details will be apparent to those of skill in the art upon reviewing the
above description. The scope of the invention should be, therefore,
determined with reference to the appended claims, along with the full
scope of equivalents to which such claims are entitled. In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein," respectively. Moreover, the terms "first," "second," and
"third," etc., are used merely as labels, and are not intended to impose
numerical requirements on their objects.